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AUTOMOTIVE 
MAGNETO     IGNITION 

ITS 

PRINCIPLE  AND  APPLICATION 

WITH 

SPECIAL  REFERENCE   TO  AVIATION  ENGINES 


BY 


MICH.  E.  TOEPEL 

\A 

Member  Society   Automotive   Engineers 

Instructor  V.  S.    Government  School  for  the  Study  of 

Magneto  Ignition 


FIRS  To-  .EDITION 


NEW    YORK   : 

SPON  &  CHAMBERLAIN,    120  LIBERTY  ST. 

LONDON   : 

E.  &  F.   N.  SPON,  LTD.,   57  HAYMARKET,  S.  W. 
1918 


.1 


Copyrighted  1918 
MICH.    E.    TOEPEL 

ALL    RIGHTS    RESERVED 


Barr  &  Hayfield,  Inc.,  Printers,  157-159  William  St.,  New  York 


PREFACE 


In  compiling  this  work  it  has  been  the  endeavor 
to  provide  a  ready  reference  on  the  subject  of 
magneto  ignition  as  applied  to  automotive  engines. 

The  rapid  expansion  of  the  practical  application 
of  electricity  for  the  purpose  of  ignition  renders  it 
difficult  to  give  a  concise  description  of-  all  details 
involved,  consequently  this  work  treats  principally 
on  the  most  efficient  type  of  ignition,  namely,  the 
magneto. 

There  is  no  doubt  that  one  of  the  influential 
factors  in  the  development  of  aviation  engines  is 
due  to  the  remarkable  efficiency  and  reliability  of 
modern  magneto  ignition.  It  has  demonstrated  that 
the  super-power  developed  by  the  present  day 
aviation  engines  is  possible  on  account  of  the  un- 
failing spark  which  nothing  but  a  magneto  can 
produce. 

The  superiority  of  magneto  ignition  in  this  field 
stands  out  prominently  inasmuch  as  that  one  of 
the  cardinal  features  is  that  it  is  entirely  self- 
contained,  requiring  but  a  small  amount  of  energy 
from  the  engine  to  produce  a  powerful  spark. 

It  was  decided  to  publish  this  work  in  the  form 
of  a  questionaire,  in  order  that  the  reader  may 
easily  grasp  the  principles  of  a  complex,  but  in- 


VI  PRKFACE 

teresting  subject.  Another  advantage  is  thereby 
obtained,  that  any  particular  subject  may  be  easily 
referred  to. 

The  author  has  had  twenty-one  years  of  practical 
experience  in  the  ignition  field,  in  addition  acting 
as  Instructor  of  the  T.  S.  Government  Magneto 
Instruction  School. 

It  has  been  the  endeavor  of  the  author  to  avoid 
reference  to  any  specific  type  of  apparatus  and 
minute  details  for  several  reasons — partly  because 
the  object  of  this  work  is  to  set  forth  the  general 
principles  oi  magneto  ignition,  also  because  any 
detail  desired  may  be  obtained  in  the  literature 
provided  by  the  manufacturers  of  ignition  devices. 

It  would  be  impossible  to  give  in  the  compass 
of  this  volume  a  description  of  every  modification 
and  avoid  confusion  by  the  elaboration  of  small 
features. 

The  knowledge  of  the  principles  of  ignition  in- 
volves the  study  of  many  diverse  subjects,  as  bat- 
teries, carburetors,  etc.,  consequently  the  informa- 
tion contained  herein,  except  when  referring  to 
aviation  engines,  is  equally  applicable  to  other  auto- 
motive engines  of  the  internal  combustion  type. 


New  York 
April  15,  1918. 


LIST  OF  ILLUSTRATIONS 


PAGE 

Symbols    Frontispiece 

Angularity,  Vee  engine,  45  degrees 76 

Angularity,  Vee  engine,  90  degrees ' 74 

Battery  timer  circuit  diagram 68 

Battery  timer  ignition,  cross  connected,  Vee  engine....  93 

Buzzer  test  set 66 

Cross  section  spark  plug,  airplane  type  48 

Cross  section  spark  plug,  rotary  engine  type 44 

Current  path,  armature  type  magneto 4 

Current  path,  polar  inductor  magneto 14 

Cylinder,  rotary  engine 62 

Distributor,  jrotary  engine ••  .  91 

Dry  batteries,  connected  multiple  series 60 

Firing  order,  Curtiss  OX2  engine 95 

Firing  order  Hispano-Suiza  engine  , 94 

Firing  order,  Sturtevant  engine  96 

Flame  propagation  around  spark  plug  electrodes 72 

Flux  path,  inductor  magneto 17 

Flux  path,  polar  inductor  magneto 18 

Formula  for  the  calculation  of  magnetizing  coils 32 

High-tension  starting  magneto   19 

Hydrometer  syringe   56 

Internal  circuit  diagram,  high-tension  magneto 42 

Internal  wiring  plan,  synchronized  magnetos  and  control 

switch  24 

Magnetizing    coils    34 

Magneto  ignition,  cross  connected,  Vee  engine 88 

Magneto  ignition,  single  spark,  Vee  engine 78 

Magnetic  field,  bar   magnet    26 

Magnetic  field,  like  poles  repel 28 

Magnetic  field,  unlike  poles  attract 29 

Magnetic  field,  wire  helix  30 


Vlll  LIST    OF    ILLUSTRATIONS 

Magneto  ignition,  two  spark.  Vee  engine 82 

Magneto,  rotary  engine   90 

Oscillogramms     40 

Position  of  carbon  brush  on  distributor 21 

Relation  of  spark  advance  to  piston  travel 84 

Rotary  engine,  position  of  pistons  and  connecting  rods.  .  92 

Rotating  circuit  breaker  20 

Rotor  and  winding,  inductor  magneto 16 

Section,  lead  plate  storage  battery 52 

Section,  nickel-iron,  storage  battery .- 54 

Sparks 1 

Stationary  circuit  breaker  22 

Stray  magnetic  field,  armature  diagonal    12 

Stray  magnetic  field,  armature  horizontal     6 

Stray  magnetic  field,  armature  reversing    10 

Stray  magnetic  field,  armature  vertical    8 

Valve  and  ignition  timing,  airplane  engine 80 

Wire  helix,  absence  of  magnetic  field 31 

Wiring  plan,  storage  battery  charging  circuit 58 


Magneto  sparks  over  a  6  m/m,air  gap. 

1.  What  is  implied  by  the  term  ignition? 

The  ignition  of  a  combustible  body  is  the  result 
of  a  form  of  kinetic  energy  in  which  molecular 
movement  takes  place,  these  violent  molecular 
movements  produce  heat  and  a  corresponding  rise 
in  temperature,  which  if  continued,  will  cause  the 
body  to  glow  and  the  emission  of  light  begins  in 
the  form  of  red  rays,  this  continues  until  a  point 
is  reached  where  inflammation  is  affected, 

2.  What  is  necessary  to  produce  ignition? 

In  every  form  of  ignition  ;  means  must  be  used 
to  permit  the  kinetic  molecular  energy  to  develop 
sufficient  heat  to  cause  the  rise  in  temperature 
necessary  to  produce  ignition,  this  is  only  possible 
through  the  expenditure  of  energy  in  some  form. 
It  is  evident  that  ^the  principle  of  ignition  depend^ 
upon  the  development  of  heat. 


3.  What  is  the   evolution  of  combustion? 

The  potential  forms  of  heat  and  light  when 
simultaneously  produced  may  be  called  inflamma- 
tion, 'and  the  physical  change  which  produces  this 
effect  is  called  ignition. 

4.  How  many  sources  of  energy  will  produce  ignition? 
There  are   four   forms  of   energy  known  at  the 

present  time,  namely,  mechanical,  caloric,  chemical 

1 


XUTO.Ut/n  YK     \I\C\KTU     IGNITION 


and    electrical,    any    of    which    may    be    utilized    to 
produce  ignition. 

5.  What  are  the  advantages  of  electricty  in  producing 

ignition? 

Electricity  on  account  of  its  wonderful  flexibility 
has  the  advantage  that  it  may  be  produced  according 
to  requirements  and  caused  to  appear  in  any  desired 
form,  at  any  place  and  be  altered  to  suit  the  purpose 
in  the  best  manner. 

6.  What  is  energy? 

The  power  of  doing  work. 

7.  What  is  potential  energy? 
The  capacity  for  doing  work. 

8.  What  is  Kinetic  Energy? 

That  which  applies  to  the  energy  of  motion. 

9.  What  is  the  theory  of  electricity? 

Electricity  exists  in  a  passive  state  in  everything. 
scientists  say  that  the  atoms  which  build  up  every- 
thing are  composed  of  two  different  elements — 
called  electrons — one  kind  being  positive,  while  the 
others  are  termed  negative.  In  the  ordinary  coursi- 
they  neutralize  one  another  and  if  electricity  is  to 
he  utilized  it  is  necessary  to  separate  the  negative 
from  the  positive  electrons,  when  a  current  will  be 
caused  to  flow.  It  is.  however,  easier  to  set  elec- 
tricitv  in  motion  in  some  substances  than  in  others. 
Copper  and  most  metals  for  instance,  the  electrons 


AUTOMOTIVE    MAGNETO    IGNITION 


move  without  much  difficulty  and  they  are  known  as 
conductors.  in  hard  rubber,  air,  there  is  great 
resistance  and  they  are  known  as  non-conductors, 
here  it  may  be  pointed  out  that  there  is  a  great 
difference  between  electricity  and  a  .  current  of 
electricity.  The  distinction  may  be  made  clear 
by  an  analogy.  We  live  surrounded  by  the  at- 
mosphere, but  normally  we  are  unaware  of  its 
presence  until  there  is  a  change  in  the  conditions 
when,  pressure  is  brought  to  bear,  and  a  wind  is 
caused  to  rise  which  we  feel.  Similarly  electricity 
remains  unnoticed  until  it  is  set  in  motion. 

There  are  several  ways  of  setting  electricity  in 
motion,  one  of  the  methods  of  exciting  an  electric 
current  is  by  utilizing  the  properties  of  magnetism 
in  electric  induction  produced  by  the  motion  of  a 
conductor  or  wire  past  a  permanent  magnet  or  of  a 
magnet  past  a  conductor. 

10.  What  are  molecules  and  atoms? 

Molecules  are  tiny  masses  of  any  substance  which 
contain  the  same  properties  of  the  substance.  Atoms 
are  still  smaller  divisions. 

11.  What  is  the  theory  of  a  magneto? 

In  the  first  place  we  have  to  form  a  conception' 
that  every  magnet  is  surrounded  by  lines  of  force 
radiating    from    the    poles,    which    form    catenary 
curves  that  become  mbre  open  and  diffused  as  the 
distance  from  the  poles  becomes  greater. 

Second — that  any  conductor  or  wire  moved  so  as 
to  cut  the  lines  of  force  is  affected  by  them,  con- 


AUTOMOTIVE    MAGNETO    TGXIT1OX 


sequently  a  current  is  set  up  in  the   wire  at  right 
angles  to  the  direction  of  motion. 

Third — the  intensity  of  the  current  thus  generated 
is  dependent  upon  the  number  of  lines  of  force  cut 
in  a  given  time,  or.  what  amounts  to  the  same 
thing,  to  the  strength  of  the  magnets  and  to  the 
rapidity  of  motion. 


Current  path,  armature  type  magneto. 


A — Armature. 

P — Primary  winding. 

R — Condenser. 

s — Hollow  shaft. 

S — Secondary  winding,  to  collector 

B-BB — Ground  brushes. 

X — Breaker  lever,  carrying  platinum  contact. 

W — Primary  and  condenser  connection. 

C — Circuit  breaker   fastening  screw. 

Y — Platinum  contact  screw. 

G — Primary  and   secondary  ground. 

The  primary  current  flows  from  ground  through  the 
primary  winding  to  the  circuit  breaker,  back  to  ground. 

The  secondary  or  high-tension  current  flows  from  ground 
through  the  secondary  winding  to  the  distributor,  to  the 
spark  plugs,  to  ground.  • 


AUTOMOTIVE    MAdXKTO    IGXITIOX  3 

Fourth — that  the  most  convenient  form  on  which 
the  conductor  or  wires  can  be  arranged  in  order 
to  maintain  a  continuous  motion,  is  that  of  a 
cylindrical  body,  such  as  an  armature. 

Fifth — that  instead  of  generating  current  as  in 
the  armature  method,  a  means,  such  as  rotating 
masses  of  iron  acting  inductively  upon  a  stationary 
winding  may  be  employed. 

12.  What  is  a  magneto? 

A  mechanical  device  for  generating  electric  cur- 
rent to  ignite  the  gaseous  mixture  in  the  cylinders 
of  internal  combustion  engines. 

12-A     What  is  the  cycle  of  electric  current  as  applied  to 
a  magneto? 

-  The  series  of  changes  through  which  the  current 
repeatedly  passes  in  one  revolution  of  the  armature. 

12-B     What  is  induction  as  applied  to  a  magneto? 

An  electric  current  produced  in  a  conductor  by 
the  variation  of  the  magnetic  field  in  its  vicinity. 

13.  What  is  a  high  tension  magneto? 

A  high-tension  magneto  is  self-contained,  that 
is;  it  has  both  the  primary  and  secondary  winding, 
necessary  for  the  production  of  the  spark,  either 
wound  on  a  shuttle  type  of  armature  or  the  primary 
and  secondary  winding  may  be  stationary  as  in  the 
inductor  type  magneto. 


AUTOMOTIVE     MACNKTO 


Stray  magnetic  tick!  in  an  armature  type  magneto,  the 
armature  in  a  horizontal  position,  the  magnetic  flux  flow- 
ing from  the  north  pole  at  the  right  to  the  south  pole. 


AI'TOAIOTlVi:     M. \r.\FlTO     K'iXITION  / 

14.  What  is  meant  by  the  term  high-tension? 

The  induced  current  of  the  secondary  winding. 

15.  What    are    the    principal    parts    of    a    high-tension 

magneto? 
Magnets,  winding,  circuit  breaker  and  condenser. 

16.  What  is   magneto-electricity? 

Electricity  which  is  produced  by  the  motion  of 
;t  magnet  past  a  conductor  or  that  of  a  conductor 
;»ast  a  magnet. 

17.  What  is  the  principle  of  operation  of  a  magneto? 
When    the   armature    rotates,    the    instrument   is 

designated  as  a  rotating  armature  type  of  magneto, 
— except  when  special  pole  shoes  are  employed — 
the  flux  reversals  occur  every  180  degrees  and  the 
magneto  generates  two  sparks  per  revolution. 

When  the  iron  core  is  fixed,  the  rotor  which  is 
of  iron  and  is  so  disposed  that  every  90  or  180 
degrees — depending  on  the  number  of  sparks  per 
revolution — the  flux  flowing  from  the  north  pole 
of  the  magnet  to  the  south  pole — through  the  rotor 
—is  suddenly  reversed. 

18.  What  is  the  cycle  of  operation  in  a  high-tension 

magneto? 

The  cycle  of  operations  in  a  high-tension  magneto 
are  as  follows,  the  rapid  reversals  of  flux  in  the 
iron  core  induce  in  both  primary  and  secondary 
winding  an  alternating  electro-motive  force,  the 
maximum  being  reached  for  any  given  speed  when 
the  actual  flux  in  the  iron  core  is  substantially  zero 
The  cam  operating  the  breaker  lever  is  so  designed 
that  the  primary  circuit  is  closed  during  the  period 


AUTOMOTIVE    MAGNETO    IGNITION 


Stray  magnetic  field  of  an  armature  type  magneto,  arma- 
ture is  in  a  vertical  position,  the  magnetic  flux  is  at  zero 
through  the  winding,  as  the  polarity  of  the  armature  is 
about  to  reverse. 


AUTOMOTIVE    M. \GNKTO    IGNITION 


when  the  induced  voltage  is  growing  from  zero 
to  its  maximum  value,  and  for  some  little  time 
afterwards,  but  not  until  the  voltage  has  become 
zero  again. 

During  the  period  of  closing  the  primary  circuit 
the  induced  current  rises  steadily  in  value.  Then 
at  a  predetermined  instant  the  contacts  are  suddenly 
separated  by  the  cam.  The  condenser  is  in  parallel 
with  the  contacts  and  insures  that  there  is  no  arcing 
at  the  contacts  at  this  instant,  consequently  the 
rupture  of  the  primary  current  is  almost  instan- 
taneous. 

The  sudden  rupture  of  the  primary  current  causes 
an  instantaneous  collapse  of  the  magnetic  field,  and 
as  the  field  is  surrounded  with  secondary  turns, 
an  enormous  voltage  is  induced  in  the  secondary 
winding  at  this  instant.  This  voltage  is  sufficient 
to  cause  a  spark  to  jump  between  the  electrodes 
of  the  spark  plug,  and  this  spark  is  maintained  to 
some  extent  by  the  voltage  induced  in  the  secondary 
by  the  reason  of  the  continual  flux  change  in  the 
iron  core  produced  by  the  rotation  during  the 
period  that  the  contacts  remain  separated.  After 
a  short  interval  of  time  the  cam  permits  the  con- 
tacts to  close  again  and  the  cycle  of  operation  is  re- 
peated. 

There  is  an  important  part  of  the  magneto, 
namely,  the  condenser,  although  an  essential  part 
of  the  magneto,  plays  a  purely  subsidiary  part,  and 
if  it  were  possible  to  break  the  primary  circuit 
quickly  enough  it  would  be  unnecessary  and  the 
magneto  would  in  fact,  be  better  without  it.  The 
purpose  of  the  condenser  is  to  delay  the  production 


10 


AUTOMOTIVE    MAGNETO    IGNITION 


Stray  magnetic  lie-Id  of  an  armature  type  magneto,  the 
armature  in  a  position  when  the  contact  points  of  the  cir- 
cuit breaker  are  about  to  separate. 


.\rTOMoTivK   M.MIXKTO  ir.xmox  11 

at  the  contact  points  of  the  voltage  due  to  the  rapid 
initial  movement  of  the  lines  of  force.  If  it  were 
not  for  this  delay  the  voltage  would  be  manifested 
at  the  platinum  points  before  they  had  time  to 
separate  properly,  consequently  arcing  at  the 
platinum  points  would  ensue,  the  circuit  would  not 
be  broken  cleanly  and  sharply  and  burning  of  the 
contact  points  would  occur.  The  condenser  obviates 
this  by  absorbing  the  initial  current  rush  and  pre- 
venting the  voltage  from  building  up  to  an  ap- 
preciable value  before  the  contact  points  have  had 
time  to  separate  properly,  but  at  the  same  time 
that  it  retards  the  development  of  the  primary  volt- 
age it  retards  that  of  the  secondary  voltage  also,  so 
that'  its  capacity  should  not  exceed  the  minimum 
necessary  for  the  successful  suppression  of  the 
sparking  at  the  contact  points. 

19.     What  is  termed  the  induced  secondary  voltage  of 
a  magneto? 

Prior  to  the  occurrence  of  the  break,  a  certain 
amount  ot  energy  is  stored  in  the  primary  winding 
by  virtue  of  the  magnetic  field  associated  with  the 
current  induced  in  the  winding  by  rotation.  The 
•magneto  is  so  designed  that  at  the  instant  when 
the  contacts  separate,  this  energy  can  be  trans- 
formed magnetically  to  the  secondary  winding  to 
'reappear  at  the  electrodes  of  the  spark  plug  in  the 
form  of  a  high-tension  discharge  at  a  very  much 
higher  potential.  The  rate  at  which  the  secondary 
voltage  rises  and  the  maximum  value  reached 
are  dependent  on  the  primary  current  broken,  on 
the  self-induction  of  the  primary  at  the  time  of  the 


12 


Stray  magnetic  field  in  an  armature  type  magneto,  arma- 
ture has  advanced  about  45  degrees,  the  magnetic  flux  pass 
in  through  the  winding. 


ACTOMOTIVK     MAGXKTO     IGXITIOX  13 


break,  on  the  ratio  of  turns  of  wire,  and  on  the 
characteristics  of  the  magnetic  circuit.  In  other 
words  it  is  necessary  that  the  magnetic  field  created 
by  the  primary  current  shall  instantly  collapse  at 
the  time  of  the  break.  Obviously,  the  rate  at  which 
the  magnetic  held  disappears  is,  other  things  being 
equal,  vital Iv  dependent  upon  the  characteristics  of 
the  magnetic  circuit  through  which  this  magnetic 
held  is  passing.  This  means  that  the  magnetic 
circuit  that  is  completely  laminated  will  insure  a 
more  rapid  dying  a\vav  of  the  magnetic  field  than 
would  occur  if  there  are  in  the  magnetic  field  any 
solid  masses  in  which  eddy  currents  may  be  set 
up  during  the  period  of  change,  these  eddy  currents 
by  their  reaction  tending  to  retard  the  rate  at 
which  the  collapse  of  the  magnetic  lines  occurs. 

20.     What  are  the  principles  of  magneto  ignition? 

The  function  of  the  magneto  is  to  produce  the 
ignition  of  an  explosive  charge  in  the  cylinder  of 
an  internal  combustion  engine. 

It  is  possible  to  regard  the  spark  given  by  a 
magneto  or  other  electric  appliance  as  being  simply 
a  small  source  of  intense  heat  and  the  rate  of  flame 
propogation  in  an  engine  cylinder  depends  to  an 
appreciable  extent  on  the  available  energy  in  the 
ignition  spark  and  consequently  the  horse  power 
developed  in  an  engine,  provided  the  spark  is  of 
sufficient  intensity  to  insure  good  ignition,  but  if 
the  mixture  is  too  weak  and  the  spark  intensity  is 
too  low,  misfiring  may  occur,  in  which  case  the 
horse  power  drops  off. 

Under  starting  conditions,  however,  the  problem 


14 


AUTOMOTIVE    MAGNETO    K'.MTION 


Current  path,  polar  inductor  magneto. 


AUTOMOTIVE    MAGXKTO    IGNITION  15 


is  more  difficult,  as  it  certainly  requires  more  energy 
to  ignite  a  cold  gas  than  a  hot  one,  especially  if  the 
fuel  used  is  rather  heavy  so  as  to  be  present  in 
the  cylinder  in  the  form  of  a  spray  or  mist  rather 
than  a  vapor. 

Let  us  therefore  consider  the  magneto  as  an  in- 
strument which  has  for  its  main  object  the  sudden 
liberation  of  a  definite  amount  of  energy  in  the 
engine  cylinder  in  the  form  of  a  spark. 

This  energy,  which  is  derived  in  the  first  instance 
from  the  mechanical  energy  given  by  the  engine 
is  transformed  in  the  magneto  itself  into  electrical 
energy,  and  transformed  back  into  heat  energy  at 
the  spark  plug,  and  we  have  to  consider  in  detail 
the  means  by  which  a  magneto  transforms  mechan- 
ical into  electrical  energy. 

This  electrical  energy  is  produced  by  means  of 
electro-magnetic  induction.  This  means  that  if  a 
conductor  is  moved  in  a  magnetic  field  an  electro- 
motive force  is  produced  in  it,  if  the  conductor  or 
wire  -form  portion  of  a  closed  circuit,  an  electric 
current  will  flow  in  this  circuit. 

The  essential  parts  of  a  magneto  are,  first,  a 
magnet,  second,  a  winding,  third,  a  circuit  breaker, 
fourth,  a  condenser. 

It  is  the  function  of  the  primary  winding  to 
produce  the  rapid  change  of  flux  \vhich  is  necessary 
to  induce  in  the  secondary  winding  a  voltage  of 
sufficient  intensity  for  the  production  of  the  spark. 
We  have  already  stated  that  if  a  magnet  be  moved 
past  a  conductor  or  wire  so  as  to  cut  the  lines  of 
force  a  voltage  will  be  induced  in  it,  and,  that  if 
the  conductor  or  wire  forms  portion  of  a  circuit 
an  electric  current  will  flow  in  it. 


16 


AUTOMOTIVE    MAGXRTO    IGXITION 


21.     What  is  a  low-tension  magneto? 

In  this  type  there  is  but  one  winding  and  requires 
a  transformer  to  step  the  low-tension  current  to 
high-tension  or  the  low-tension  current  may  be 
used  direct  for  make  and  break  ignition. 

22.     What  is  the   principle   of   a   low-tension   magneto 
with  a  transformer? 

In  a  high-tension  system  of  ignition  employing 
a  low-tension  magneto,  the  principle  of  operation 
is  based  on  the  extra  current  produced  at  the 
moment  of  opening  of  the  platinir.n  points  of  the 
circuit  breaker. 


Rotor  and  winding  of  an  inductor  magneto. 
The  winding-  is  stationary  and  the  rotor  blocks  revolve. 

23.     What  is  an  inductor  type  magneto? 

In  this  type,  the  magnetic  flux  is  made  to  pass 
through  a  stationary  winding,  first  in  one  direction 
and  then  in  reverse  way.  an  alternating  electro- 
motive force  will  be  produced,  and,  if  the  terminals 
of  the  winding  are  connected  to  an  outside  resistance. 
current  will  flow.  In  the  principle  of  the  inductor 


A  I'TM  MOTIVE    MAGXETO    IGNITION  17 


magneto,  the  current  is  induced  in  its  winding  in- 
stead of  being  generated  in  the  winding  when  a 
winding  is  moved  so  as  to  cut  the  lines  of  magnetic 
force. 

24.     What  is  a  polar  inductor  type  of  magneto? 

\Yhen  a  rotor  comprises  iron  masses  of  a  fixed 
or  constant  polarity  operating  in  conjunction  with 
an  iron  core  carrying  the  windings,  the  instrument 
is  designated  as  a  polar  inductor  type  of  magneto. 


Flux  path  of  an  inductor  magneto,  a  reversal  of  mag- 
netic flux  occurring  every  90  degrees. 

The  path  of  the  magnetic  flux  is  indicated  by  the  arrows 
and  flows  from  one  pole  piece  at  the  base  of  the 
magnets,  through  one  half  of  the  rotor  block,  through  the 
winding,  through  the  opposite  rotor  block  to  the  opposite 
pole  piece.  .  When  the  rotor  has  moved  90  degrees,  the 
opposite  faces  of  the  rotor  will  again  be  presented  to  the 
pole  pieces,  but  the  magnetic  flow  will  be  in  the  opposite 
direction  and  causes  the  magneto  to  produce  an  alternat- 
ing current. 

25.     What  is  a  two  spark  magneto? 

A  magneto  provided  with  two  distributors,  con- 
nected to  each  end  of  the  secondary  winding,  de- 


18 


AUTOMOTIVE    MAGNETO    IGNITION 


signed  to  produce  two  sparks  simultaneously  at 
two  different  spark  plugs  in  the  same  engine  cyl- 
inder. 


26.     What  is  a  sleeve  inductor  magneto? 

A  magneto  which  embodies  a  stationary  shuttle 
type  armature  surrounded  by  a  rotating  sleeve. 
The  movement  of  the  rotating  sleeve  produces  a 
change  of  magnetic  flux  through  the  stationary  ar- 
mature every  90  degrees,  consequently  4  sparks  are 
produced  every  revolution. 


Flux  path  of  a  polar  inductor  magneto,  a  reversal  uf 
magnetic  flux  occurring  every  180  degrees. 

The  rotating  poles  N,  S  are  always  of  the  same  polarity, 
when  N  is  opposite  G,  the  flux  flows  from  N  to  G,  through 
the  core  of  the  winding  C  to  F,  to  S. 

In  the  second  figure  the  pole  X  has  moved  over  to  F 
and  the  direction  of  the  flow  of  flux  is  reversed  and  flows 
from  N  to  F,  through  C  to  G,  to  S. 

In  the  third  figure  the  rotating  poles  occupy  a  midway 
position,  here  the  field  pieces  F  and  G  are  magnetically 
short  circuited,  scavenging  stray  lines  of  flux  out  of  tin- 
core  C. 

27.     What   is   meant   by   the    term    Synchronized    Mag- 
netos? 

The  occurrence  of  two  sparks  from  two  mag- 
netos simultaneously  in  the  cylinder  of  an  engine. 


AUTOMOTIVE    MAGNETO    IGNITION  19 


28.     What  is  a  fixed  spark  magneto? 

A  magneto  in  which  the  relation  of  the  magnetic 
break  of  the  rotating  element  with  the  mechanical 
oieak  of  the  contacts  is  in  a  fixed  position,  it  has 
no  timing  lever. 

28- A.    What  is  a  unidirectional  magneto? 

A  high  tension  magneto  that  produces  sparks  of 
one  polarity  only.  There  are  four  magnetic  breaks 
writhin  the  magneto,  but  owing  to  a  modification  of 
the  cam  only  two  sparks,  both  of  the  same  polarity, 
are  produced.  In  the  ordinary  magneto  the  current 
being  alternating,  sparks  of  negative  and  positive 
polarity  are  produced. 


High-tension    starting   magneto   for  airplane  engines. 

28-B.     What  is  a  starting  magneto? 

It  is  a  small,  geared  up  hand  cranked  magneto 
operating  as  an  auxiliary  scource  of  high-tension 
current,  whereby  a  shower  of  sparks  may  be 
generated  to  produce  ignition  in  the  cylinder  about 
to  fire,  through  the  medium  of  a  trailing  pin  in 


20 


the  distributor  which  is  set  a  number  of  degrees 
later  than  the  main  distributor  and  operates  in 
conjunction  with  it. 

28-C.     How  does  the  secondary  current  flow  in  a  high- 
tension  magneto? 

When  the  high-tension  current  emanating  from 
the  magneto  passes  through  the  center  electrode 
of  the  spark  plug  to  the  engine  it  is  termed  positive, 
the  high-tension  current  Mowing  from  the  grounded 
end  of  the  secondary  winding,  through  the  magneto 
frame,  engine,  spark  plug  shell  to  the  center  elec- 
trode, cable,  to  the  magneto,  the  current  is  termed 


Rotating'  circuit  breaker  with  internal  cams. 

29.  What  is  a  circuit  breaker? 

A  circuit  breaker  is  a  mechanical  device  for 
opening  and  closing  the  primary  circuit,  having 
one  stationary  contact  and  one  cam  acuated  move- 
able  contact. 

30.  How  does  a  circuit  breaker  operate? 

The  contacts  are  either  mounted  on  a  rotating 
plate  and  actuated  by  one  or  more  cams  fixed  in 
a  housing,  or  the  contacts  may  be  fixed  on  a 
movable  plate  and  actuated  by  a  rotating  cam. 


AUTO-MOTIVE    MAf.XETO    IGNITION  21 


31.     What  effect  has  the  rapid  breaking  of  the  primary 
circuit  upon  the  secondary? 

It  has  been  shown  by  experiment,  that  when  the 
primary  circuit  is  broken  by  shooting  a  bullet 
through  a  wire,  it  is  possible  to  attain  a  long 
secondary  spark  without  a  condenser  across  the 
primary  circuit.  \Yith  a  mechanical  circuit  breaker 
the  rapidity  of  the  break  is  limited  by  the  imperfec- 
tion of  the  circuit  breaker  and  it  becomes  necessary 
to  use  a  condenser  to  prevent  the  destructive  arcing 
across  the  contact  points. 


RI6HT  WRONG  WRONG 

Position  of  carbon  brush  on  distributor,  contacts  open- 
ing, timing  lever  fully  advanced.  The  brush  should  be 
full  on  the' segment,  otherwise  the  highly  finished  surface 
of  the  distributor  will  become  pitted  and  burnt. 


32.     What  is  a  distributor? 

.  A  block  of  insulating  material  having  a  number 
of  segments  or  carbon  brushes,  equal  to  the  number 
of  cylinders  to  be  fired,  an  insulated  distributing 
member  fitted  with  a  brush  or  segment  by  means 
of  which  the  high-tension  current  is  distributed  to 
the  cylinders  in  their  proper  firing  sequence. 


22  AUTOMOTIVE  :\i  \ < ; x  i-"n  >   H;\ITIO x 


33.     What  is  called  dual  ignition? 

Dual  ignition  uses  a  transformer  and  one  set  of 
spark  plugs  with  the  current  supplied  by  either  the 
magneto  or  a  battery,  the  circuit  breaker  and  the 
distributor  are  common  to  both.  The  magneto 
may  be  either  high-tension  or  low-tension. 


Stationary  circuit  breaker  with  rotating  cam. 

34.  What  is  called  duplex  ignition? 

Duplex  ignition  utilizes  the  battery  current  for 
starting  also  the  magneto  when  the  engine  is 
cranked.  In  this  system  the  battery  current  is 
thrown  in  phase  with  the  magneto,  the  battery 
current  passing  through  an  impedance  coil,  and  by 
means  of  a  commutator,  the  flow  of  the  battery 
current  is  made  to  flow  in  the  same  direction  as 
the  magneto  current,  that  is  inasmuch  as  the 
magneto  current  is  alternating  and  the  battery  cur- 
rent also  flows  in  the  same  direction  or  in  phase,  so 
called. 

35.  What  is  independent  ignition? 

Independent  ignition  is  a  term  usually  applied  to 
a  self  contained  magneto  that  it  is  not  connected  to 
or  dependent  on  any  auxiliary  source  of  current. 


AUTOMOTIVE    M  \C.\KTO    IGXITIOX  23 


36.  What  does  a  high-tension  system  of  ignition  con- 

sist of? 

In  a  magneto,  a  primary  winding  in  circuit  with 
a  condenser  and  circuit  breaker,  a  distributor  in 
circuit  with  the  secondary  winding,  cables  leading 
to  the  spark  plugs  and  a  switch  to  control  the  action 
of  the  magneto. 

37.  How  is  a  magneto  timed? 

A  magneto  is  timed  by  setting  the  magnetic  break 
and  platinum  contacts  correctly,  at  the  same  time 
having  the  distributor  in  full  contact  with  the  brush 
or  segment,  timing  lever  fully  advanced. 


38.     How  many  systems  of  ignition  are  there  in  use  at 
the   present  time? 

Generally  speaking,  there  is  only  one  system  in 
use  at  the  present  time,  namely,  high-tension. 


39.  How  can  one  tell  a  right  hand  or  clockwise  mag- 
neto from  a  left  hand  or  counter  clockwise  mag- 
neto? 

The  direction  of  rotation  is  usually  marked  on 
the  oil  cover  or  some  other  part  at  the  driving  end 
of  the  magneto. 


39-A     How  would  you  ascertain  the  direction  of  rota- 
tion of  a  magneto  that  was  not  marked? 

By  turning  it  and   feeling  the   magnetic   pull   in 
relation  to  the  opening  of  the  contact  points. 


24 


AUTOMOTIVE    MAGNETO    IGNITION 


40.     What  is  the  theory  of  magnetism? 

Magnetism  is  a  phase  of  molecular  motion  in 
which  the  magnetizing  process  produces  harmonious 
vibration  of  the  molecules  to  take  the  same  relative 
position  whereby  magnetic  effects  are  produced. 
\Yhen  the  magnetizing  process  ceases,  the  har- 
monious vibration  of  molecules  is  maintained  in 
hardened  steel  and  in  soft  iron  this  activity  disap- 
pears entirely. 


H  MAG/VETO 


Internal    wiring   plan,    two    synchronized    magnetos    and 
control  switch. 


41.     What  is  the  history  of  magnetism? 

It  has  been  said  and  written  that  the  ancient 
Chinese  were  acquainted  with  the  properties  of 
magnetism,  which  they  utilized  in  the  mariners 
compass.  The  Greek  shepard  Magnes — so  the 
legend  goes — was  unexpectedly  detained  by  the  iron 


AUTOMOTIVE    MAGNETO    IGNITION  25 


nails  in  his  shoes  being  held  fast  to  a  large  body  of 
lodestone  (magnetic  iron  ore)  with  which  he  ac- 
cidentally came  into  contact. 

The  fact  remains  that  the  properties  of  magnetism 
have  come  to  play  a  vital  part  in  the  ignition  of  the 
internal  combustion  engine. 

42.  What  is  a  magnet? 

A  body  possessing  the  power  of  attracting  the 
opposite  poles  of  another  magnet  or  repelling  the 
like  poles  or,  having  the  power  of  attracting  mag- 
netizable bodies  to  either  pole. 

43.  What  is  a  magnetic  field? 

The  region  of  magnetic  influence  surrounding  the 
poles  of  a  magnet.  The  magnetic  field  of  an  elec- 
tric current  is  that  which  surrounds  a  circuit 
traversed  by  an  electric  current. 

44.  What  is  a  bar  magnet? 
A  simple  magnetized  bar. 

45.  What  is  a  permanent  magnet? 

A  magnet  composed  of  hardened  steel,  which 
usually  contains  a  small  amount  of  tungsten,  and 
retains  its  magnetism  a  long  time  after  it  is  mag- 
netized. 

46.  What  is  a  horse-shoe  magnet? 

A  magnet  is  shaped  like  a  horse-shoe,  because  it 
was  found  that  the  greatest  magnetic  strength  laid 


26  AI.'TO.MOTIVK     MAC.NKTO    IGNITION 


fm 


Magnetic  field  of  a  bar  magnet,   the  catenary  curves  be- 
come longer  as   tlie  distance   from  the  poles   increases. 


AUTOMOTIVE    MAGNETO    IGNITION  27 


in  the  poles  and  its  opposite  poles  are  nearer  to- 
gether, consequently  through  the  concentration  of 
the  magnetic  lines  of  force,  the  poles  of  a  horse- 
shoe magnet  offer  the  least  resistance  to  the  flow 
of  the  magnetic  lines  of  force,  across  the  air  gap 
intervening. 

47.     What  is  a  compound  magnet? 

A  number  of  single  magnets,  placed  one  over 
another  and  with  their  similar  poles  facing  each 
other. 


48.     What  is  a  bell  shaped  magnet? 

This  is  a  modification  of  the  horse-shoe  magnet 
in  which  the  approaching  poles  are  semi-annular  in 
shape  and  form  a  split  tube. 


49.     What  is  meant  by  the  term,  magnetic  Permeability? 

I'onductibilitv  of  the  lines  of  magnetic  force. 
Iron  possesses  this  property  to  a  greater  degree  as 
it  permits  the  lines  of  magnetic  force  to  readily 
pass  through  it,  in  other  words  the  magnetic  resist- 
ance of  iron  is  low. 


49-A     What  is  called  Coercive  force  in  a  magnet? 

I  lie  power  of  resisting  magnetization  or  de- 
magntization.'  Hardened  steel  possesses  this  pro- 
perty to  a  greater  degree  and  in  soft  iron  the  co- 
ercive force  is  feeble. 


28  AUTOMOTIVE    MAGNETO    IGNITION 


50.  What  is  magnetic  saturation? 

When  a  magnetized  body  fails  to  be  further 
magnetized  no  matter  how  great  the  magnetizing 
force. 

51.  What  is  meant  by  a  magnet  being  super-saturated? 

A  magnet  is  said  to  be  super-saturated  when  it 
has  received  more  magnetism  than  it  can  retain  for 
any  length  of  time  after  it  has  been  magnetized. 


Magnetic  field  around  a  pair  of  magnets,  the  north  and 
south  poles  facing  each  other,  like  poles  repel. 

52.  What  is  implied  by  the  term  Magnetic  Flux? 

The  total  number  of  lines  of  force  flowing 
through  a  magnetic  circuit. 

53.  What  is  the  keeper  of  a  magnet? 

A  piece  of  soft  iron  placed  across  the  poles  of 
a  magnet  through  which  the  lines  of  magnetic  force 
pass. 


AUTOMOTIVE    MAGXETO    IGNITION  29 

54.  What  is  magnetic  lag? 

The  inability  of  a  magnet  core  to  instantly  lose 
its  magnetism. 

55.  What  is  magnetic  leakage? 

A  useless  dissipation  of  the  lines  of  magnetic 
force  which  fail  to  pass  through  an  armature  or 
winding. 


Magnetic  field  around  a  pair  of  magnets,  the  north  poles 
facing  the  south  poles,  unlike  poles  attract. 

56.  Define  the  power  of  magnetic  induction? 

It  is  the  power  which  a  magnet  possesses  to  de- 
velop magnetism  in  iron.  If  a  piece  of  soft  iron 
be  brought  near  a  magnet,  it  immediately  assumes 
the  magnetic  state,  which  however  it  loses  on  be- 
ing removed  from  the  magnetic  influence. 

57.  What  is  meant  by  the  term  Magnetic  Attraction? 
The  attracting  power  of  a  magnet  when  a  piece 


30  A U T( ) M  <  >T  I V K     M  . \ ( ;  \  KT(  >    1  ( ;  N  IT  I  < > X 


of    iron    is   brought    within    the    lines    of    magnetic 
force  of  a  magnet. 

58.  What  is  meant  by  the  term  Magnetic  Traction? 

The  force  by  which  a  keeper  is  kept  in  contact 
with  a  magnet. 

59.  What  are  Magnetic  Poles? 

Those  members  of  a  magnetic  scource  at  which 
the  flux  enters  or  leaves. 


.        , 


Helix  of  wire  traversed  by  an  electric  current,  a  mag- 
netic field  is  created  within  the  helix  and  the  lines  of  force 
circulate  around  each  turn  of  wire. 

60.  What  are  the  pole  pieces  of  a  magneto? 

Pieces  of  iron  placed  inside  of  the  permanent 
magnets  to  define  and  limit  the  magnetic  field. 

61.  How   would   you   determine    the    North   pole    of   a 

magnet,  if  it  was  not  marked  or  a  compass  was 
unavailable? 

The  north  pole  of  a  magnet  can  be  found  by 
means  of  an  ordinary  needle,  mark  one  of  the 


AUTOMOTIVE    MAGNETO    IGNITION  31 


magnet  poles  and  rub  the  point  of  the  needle  on  the 
marked  pole,  rub  the  eye  of  the  needle  on  the  other 
magnet  pole,  suspend  the  needle  from  a  light  thread 
or  float  it  on  a  disc  of  cork  in  a  glass  of  water,  the 
needle  will  then  point  north.  If  the  sharp  end  of 
the  needle  points  north  then  the  marked  pole  of  the 
magnet  is  of  south  polarity  and  if  the  sharp  end  of 
the  needle  points  south,  the  marked  pole  of  the 
magnet  is  of  north  polarity. 


v       ft 


liii 


Helix  of  wire,  note  the  absence  of  magnetic  lines  of 
force  when  no  current  is  passing  through  the  helix. 

62.  How   would   you   determine   the   north   pole   of  an 
electro-magnet? 

If  a  bar  of  iron  with  a  coil  of  wire  on  it  is  held 
before  the  dial  of  a  clock,  with  one  end  of  the  bar 
pointing  toward  the  dial,  and  the  current  flowing 
through  the  wire  in  the  direction  of  rotation  of  the 
hands  of  the  clock,  then  the  lines  of  magnetic  force 
will  flow  through  the  bar  toward  the  clock.  The 
north  pole  will  be  next  to  th»j  clock. 

63.  What  is  an  electro-magnet? 

A  magnet  produced  by  the  flow  of  a  direct  cur- 


32  . 


AUTOMOTIVE    MAGXKTO    IGXITIOX 


Formula  for  the  calculation  of  magnetizing  coils. 


AUTOMOTIVE    MAGXETO    IGNITION  33 


rent  through  a  coil  of  insulated  wire  surrounding  an 
iron  core. 

64.  How  would  you  describe  a  magnetic  compass? 

A  magnetic  needle,  resting  upon  a  pivot,  enclosed 
in  a  circular  case,  the  needle  points  nearly  north. 

65.  What  kind  of  current  is  used  to  magnetize  mag- 
nets? 

Direct  current  can  only  be  used  for  this  purpose. 

66.  What  methods  are  used  to  magnetize  permanent 
magnets? 

Magnetization  may  be  effected  by  magnetic  in- 
duction from  another  magnet,  usually  a  powerful 
electro-magnet,  or  by  induction  with  a  set  of  mag- 
netizing coils  traversed  by  a  direct  electric  current 
which  is  the  best  method. 

66-A     How  would  you  determine   the   proper   way   to 
insert  a  magnet  in  a  magnetizing  coil? 

By  determining  the  north  pole  of  the  magnet  by 
a  compass  and  marking  it,  next  find  the  polarity  of 
the  magnetzing  coils  by  inserting  a  piece  of  iron  in 
it  and  switching  oh  the  current  and  find  the  polarity 
of  the  magnetized  iron  with  a  compass,  then  place 
the  magnet  in  the  coils  to  magnetize  it  in  the  same 
way  that  it  was  originally  magnetized. 

€7.     What  means  are  used   to   magnetize   magnets   by 
the  coil  method? 

.Magnets  are  magnetized  by  inserting  the  poles 
in  a  set  of  coils  wound  to  give  the  maximum  mag- 


34  AUTOMOTIVE    MAGNETO    IGNITION 


netizing  effect.  The  coils  are  usually  wound  with 
a  certain  s'ize  of  wire,  depending  on  the  charging 
current,  that  is.  depending  on  the  line  voltage  and 
rating  per  coil,  they  may  he  connected  in  series  or 
multiple.  The  accompanying  tables  give  the  relative 
size  of  wire  necessary  for  the  line  voltage  available. 
the  resistance  and  number  of  feet  of  copper  wire 
per  Ib.  Consulting  one  of  the  tables  it  will  be  found 
that  a  set  of  coils  absorb  450  watts  and  to  wind  a 
set  of  coils  for  use  on  a  110  volt  line.  Xo.  21  copper 


Magnetizing  coils,  magnet   in   position   to  he   magnetized. 

wire  should  be  used,  the  coils  drawing  450  -^  1 10  or 
a  little  over  4  amperes.  The  resistance  of  the  coils 
equals  110  -f-  4  or  27.5  ohms,  consequently  as  pet- 
table  of  copper  wire.  2200  feet  will  be  required  and 
it  follows  that  inasmuch  as  5000  ampere  turns  are 
necessary  for  each  coil,  or  1220  turns  of  Xo.  21 
copper  wire.  Similarily  a  set  of  coils  wound  for 
a  10  volt  line  would  draw  45  amperes,  requiring  (tf» 
turns  of  Xo.  10  wire,  or  220  feet.  It  must  be  borne 
in  mind  that  the  flow  of  current  to  fully  magnetize 
a  magnet  is  only  a  few  seconds. 


35 


Table-  showing  resistance  and  feet  per  pound  of 
copper  wire. 


Brown  &  Sharpe 
wire  gauge  Xo. 

Feet 
per  11). 

Ohms  per 
1000  ft.  68°  F. 

10 

32 

1. 

11 

40 

1.2607 

12 

51 

1.5898 

13 

64 

1.995 

14 

81 

2.504 

15 

102 

3.172 

16 

\Z9 

4.001 

17 

162 

5.04 

18 

204 

6.36 

19 

264 

8.25 

20 

325 

10.12 

21 

400            12.76 

22 

517            16.25 

23 

660 

20.30 

24 

823 

25.60 

25 

1029           32.20 

26 

1310           40.70 

27 

1650           51.30 

28 

2082           64.80 

29 

2623           81.60 

30 

3311          103. 

68.     How  are  magnetizing  coils  connected  and  wired? 

C Oils  must  be  connected  together  to  produce  op- 
posite poles  when  a  magnet  is  inserted  in  them,  a 
knife  switch  that  is  fused  is  usually  placed  between 
the  charging  circuit  and  the  coils.  Each  coil  has 
two  leads  which  may  be  connected  in  series,  that  is, 
in  series  the  current  Hows  from  the  charging  circuit 
through  one  coil,  through  the  other  eoil  back  to  the 
charging  circuit,  or  the  coils  may  be  connected  in 
multiple,  that  is.  one  of  the  leads  from  each  coil  are 
connected  together,  the  combined  leads  are  then 
connected  to  the  charging  circuit,  the  advantage  of 


36  AUTOMOTIVE    MAGXKTO    IGXITIOX 


the  latter  is  apparent,  as  when  a  pair  of  coils  are 
wound  to  be  used  in  series  with  a  220  volt  circuit, 
they  may  be  connected  in  multiple  for  use  with  a 
110  volt  circuit. 


69.  What  is  an  Ampere  tarn? 

One  turn  of  a  winding  through  which  a  current 
of  one  ampere  is  flowing.  The  number  of  amperes 
multiplied  by  the  number  of  turns  in  a  winding 
equal  the  total  number  of  ampere  turns  in  a  wind- 
ing. 

70.  What  is  an  ampere  turn  as  applied  to  a  winding? 

The  equivalent  of  one  ampere  passing  through 
one  turn  of  copper  wire  surrounding  an  iron  core, 
that  is  one  ampere  carried  around  the  core  for  100 
turns  (100  ampere  turns)  will  equal  in  effect  ten 
amperes  flowing  through  ten  turns.  The  effect  of 
the  turns  decreases  with  their  distance  from  the 
core,  a  good  rule.. to  follow  is,  to  wind  the  wire 
one  .inch  deep  on  a  core  of  one  inch  in  diameter, 
or  a  total  thickness  of  three  inches. 

70-A.     How  can  the  strength  of  a  pair  of  magnets  be 
retained  when  they  are  removed  from  a  magneto? 

The  magnetic  flux  which  flows  from  the  north 
pole  to  the  south  pole  will  cause  a  pair  of  magnets 
of  unlike  poles  to  stick  together,  hence  the  rule, 
like  poles  repel  and  unlike  poles  attract,  therefore 
when  a  pair  of  magnets  are  removed  from  a  mag- 
neto they  should  at  once  be  placed  in  a  position 


AUTOMOTIVE    MAGNETO    IGNITION  37 

that  there  is  a  good  metallic  contact  between  the 
unlike  poles. 

70-B.     Why  is  an  iron  core  used  in  a  winding? 

An  iron  core  inside  of  a  winding  increases  the  in- 
ductive effect,  as  a  given  current  can  produce  more 
lines  of  force  in  an  iron  core  than  in  air. 

71.     What  is  electrical  induction? 

It  is  the  influence  of  an  electrified  body  over 
other  bodies. 

71-A.     What  is  called  the  primary  current  in  a  high- 
tension  magneto? 

The  primary  current  flows  through  the  primary 
winding  of  the  magneto  and  usually  consists  of  a 
few  layers  of  coarse  wire,  it  is  wound  next  to  the 
core. 

71-B.     What  is  called  the  secondary  current  in  a  high- 
tension  magneto? 

The  secondary  or  high-tension  current  flows 
through  the  great  number  of  turns  of  fine  wire 
wound  over  the  primary  winding  at  the  time  of  the 
passing  of  the  spark  between  the  electrodes  of  the 
spark  plug,  the  high-tension  current  is  induced  in 
the  secondary  winding  through  the  action  of  the 
circuit  breaker  interrupting  the  flow  of  primary 
current. 


38  AUTOMOTIVE    MAC.NKTO    JGXITION 


72.  What  is  the  effect  of  the  secondary  current  on  the 

iron  core? 

The  secondary  current  retards  the  demagnetiza- 
tion of  the  iron  core. 

73.  How    does    the    duration    of    the    secondary    spark 

affect   the  iron   core? 

The  duration  of  the  secondary  spark  is  inversely 
proportional  to  the  length  of  the  spark,  the  maxi- 
mum value  of  the  primary  current  being  constant. 
This  duration  explains  the  relative  slowness  of  the 
demagnetization  of  the  iron  core. 

74.  How  does  the  lag  in  a  winding  vary? 

The  amount  of  lag  varies  with  the  co-efficient  of 
self-induction,  the  capacity  and  the  current  value. 

75.  What  are  laminae  and  why  are  they  used? 

Structural  subdivisions  of  the  cores  of  armatures, 
elctro-magnets,  etc.,  to  prevent  the  loss  of  energy 
from  eddy  currents. 

76.  What  are  Eddy  Currents? 

Currents  generated  in  a  magnetized  body  by  the 
variations  of  the  strength  of  electric  currents  flow- 
ing near  them,  they  are  of  no  value  however. 

77.  What  is  residual  magnetism? 

Magnetism  remaining  in  the  core  of  a  winding- 
after  the  magnetizing  effect  has  ceased  on  the 
opening  of  the  magnetizing  circuit. 


AUTOMOTIVE    MAGNETO    IGNITION  39 


78.     What  is  hysterisis  and  its  effect  on  an  iron  core? 

Hysterisis  is  the  energy  lost  in  the  magnetizing 
and  de-magnetizing  of  iron.  An  iron  core  mag- 
netizes more  rapidly  than  it  de-magnetizes,  a  certain 
amount  of  residual  magnetism  always  remains  and 
iivsterisis  is  due  to  the  retention  of  energy.  Hys- 
terisis manifests  itself  in  the  form  of  heat,  but 
must  not  he  confounded  with  eddy  currents  which 
are  avoided  by  sub-dividing  the  iron  core,  whereas 
hysterisis  depends  upon  the  quality  of  iron  and 
length  of  the  core. 


79.     What  is  the  ratio  of  the  primary  to  the  secondary 
winding? 

The  ratio  of  primary  to  the  secondary  winding  is 
approximately  60 — 1  or  200  turns  of  primary  wire 
to  12.000  turns  of  secondary  winding. 


80.     What  is  the  size  of  wire  on  the  primary? 

The  size  of  wire  on  the  primary  varies  from  \T<>. 
19 — 24  R&S  gauge  and  is  usually  enameled,  silk- 
covered  or  both. 


81.     What  is  the  size  of  the  wire  on  the  secondary? 

The  size  of  wire  on  the  secondary  varies  from 
No.  34 — 38  B&S  gauge,  enameled  wire  is  usually 
employed,  this  insulation  does  not  occupy  much 
space,  permitting  the  winding  to  lay  nearer  to  the 
core  to  obtain  the  maximum  secondary  effect. 


40 


AUTOMOTIVE    MAGNETO    IGNITION 


Primary  voltage,  H  armature  type  magneto.     Time  be- 
tween reversals  .125  second. 


Primary  current,   H  armature  type 
tween  reversals  .125  second. 


Secondary  current  over  a  .031  spark  gap  of  high  tension 
H  armature  type  magneto.  Time  between  sparks  .125 
second. 


Primary  current,  H  armature  type  adjustable  pole  mag- 
neto.   Time  between  reversals  .055  second. 

Oscillograph  diagrams. 


41 


82.  What  is  a  coil  employing  the  principle  of  the  extra 

current  called  and  how  is  it  used? 

A  reactance  coil  for  low-tension  ignition  is  com- 
posed of  an  iron  core  and  a  number  of  layers  of 
copper  wire.  Due  to  the  inductive  action  of  the 
coil,  when  the  current  is  interrupted  by  the  action 
of  the  igniter  which  causes  the  current  to  flow 
longer  in  both  time  and  distance  across  the  gap 
formed  by  the  separation  of  the  igniter  con- 
tacts within  the  cylinder.  A  reactance  coil  becomes 
necessary  when  a  battery  is  used  to  supply  the 
current,  whereas  when  a  low-tension  magneto  is 
used,  the  inductive  action  of  the  armature  acts  in 
the  same  manner. 

83.  What  are  Oscillograph  Diagrams? 

Oscillograph  diagrams  show  in  a  graphic  way 
just  what  occurs  in  both  the  primary  and  secondary 
windings.  When  the  primary  circuit  is  closed,  the 
current  rises  gradually  in  value,  until  the  circuit  is 
broken,  no  current  will  be  induced  in  the  secondary 
circuit  during  the  period  the  primary  current  is 
attaining  its  full  value,  which  is  due  to  the  fact  that 
the  electro-motive  force  induced  in  the  secondary 
winding  during  this  period  is  not  sufficiently  great 
to  break  down  the  resistance  of  the  air  gap  at  the 
spark  plug.  The  spark  occurs  when  the  primary 
circuit  is  broken,  rising  to  its  maximum  value  in- 
stantly. 

The  oscillograph  diagrams  show  that  both  the 
electro-motive  force  and  the  current  of  a  magneto 
rise  to  a  sharp  peak,  first  in  one  direction,  then  in 
the  reverse  direction,  as  the  current  is  an  alternating 
one. 


42 


AUTOMOTIVE    .MAC.XKTO    KiN  IT1OX 


It  will  be  noticed  that  only  the  peak  of  the 
current  wave  is  utilized  for  the  production  of  the 
secondary  current,  the  maximum  current  value  be- 
ing reached  when  the  greatest  number  of  magnetic 
lines  of  force  in  the  permanent  field  of  a  magneto 
are  cut. 


Internal   circuit   diagram,   h-igh-tension  magneto. 


AUTOMOTIVE    MAGNETO    IGNITION  43 


84.     What   is   a   condenser? 

A  condenser  is  a  device  for  increasing  the  capacity 
of  an  insulated  conductor  by  bringing  it  near  an- 
other insulated  earth-connected  conductor,  but 
separated  from  it  by  a  medium  that  will  permit 
electro-static  induction  to  take  place  through  its 
mass. 


85,     What  is  the  function  of  a  condenser? 

The  function  of  a  condenser  is  to  absorb  the 
initial  rush  of  current  when  the  platinum  contact 
points  of  a  circuit  breaker  are  separated,  otherwise 
destructive  arcing  would  occur,  this  prevents  the 
rapid  rupture  of  the  primary  current,  with  a  con- 
sequent decrease  of  the  induction  in  the  secondary 
winding. 


86.     How  is  a  condenser  constructed? 

A  condenser  consists  of  a  number  of  sheets  of 
tin- foil,  separated  by  a  dielectric  of  very  thin  sheets 
of  mica  or  a  special  grade  of  paper.  Each  alter- 
nate sheet  of  tin- foil  extends  beyond  the  edge  of 
the  insulating  material,  these  are  pressed  together 
so  as  to  make  electrical  connection  between  them 
and  form  one  side  of  the  condenser,  the  sheets  of 
tin-foil  projecting  from  the  opposite  side  are  also 
pressed  together,  forming  the  other  side  of  the 
condenser.  The  finished  condenser  is  usually  im- 
pregnated with  a  varnish  or  Other  insulating  com- 
pound and  pressed  to  exclude  moisture. 


44  AUTOMOTIVE    MAGNETO    IGNITION 

87.  What  is  meant  by  the  dielectric  in  a  condenser? 

The  insulating  medium  of  a  condenser  which 
separates  the  sheets  of  tin- foil  and  permits  induc- 
tion to  take  place  through  its  mass. 

88.  What  part  of  a  condenser  retains  the  charge? 

The  charge  of  a  condenser  remains  on  the  op- 
posite surfaces  of  the  dielectric  separating  the  tin- 
foil. 


Cross  section,  spark  plug,  rotary  engine  type. 

89.     What  is  meant  by  a  condenser  discharge? 

The  equalization  of  the  difference  of  potential 
from  its  maximum  to  zero,  when  the  terminals  of  a 
condenser  are  connected  by  a  conductor. 

89-A  What  is  the  action  of  the  condenser  on  the 
primary  winding  after  the  contact  points  have 
separated? 

The  charge  impressed  upon  the  condenser  by 
absorbing  the  extra  current  at  the  contact  points  in 
the  moment  of  the  opening  of  the  primary  -circuit  is 


AUTO  MOT!  VI-:    MAC.XKTO    K1XITIOX  45 


returned  to  the  primary  winding  when  the  contacts 
come  together  in  the  form  of  a  current  of  about  40 
volts  and  ]/?  milli-ampere. 

90.  How  is  the  capacity  of  a  condenser  measured? 

The  capacity  of  a  condenser  is  measured  in  micro- 
farads. 

91.  How   can  you  test   a   condenser,   also    ascertain   if 

it  holds  its  charge  or  leaks? 

By  comparing  it  with  a  standard  condenser.  Con- 
nect the  condenser  to  be  tested  in  series  with  a 
milli-ammeter  and  place  the  terminals  of  a  test  line 
on  one  of  the  terminals  of  the  condenser  and  the 
other  on  one  of  the  terminals  of  the  meter,  the 
deflection  of  the  meter  depends  upon  the  condition 
of  the  condenser,  the  more  the  deflection,  the  less  the 
charge,  as  a  greater  deflection  than  shown  by  a 
standard  condenser .  denotes  a  leak  which  permits 
the  current  to  flow  through  the  condenser.  The 
milli-ammeter  should  be  one  of  a  low  range  or 
reading,  with  the  pointer  in  the  center,  the  scale 
calibrated  to  read  5-0-5  milli-amperes.  When 
charging  the  condenser,  the  pointer  will  be  deflected 
to  one  side  of  the  scale,  on  discharge  the  pointer 
will  be  deflected  to  the  other  side  of  the  scale  on 
the  meter. 

92.  What  is  a  micro-farad? 

A  micro-farad  is  the  millionth  of  a  farad.  A 
condenser  of  a  capacity  of  one  micro-farad  will 
contain  about  3600  square  inches  of  tin-foil.  Con- 


46  AUTO  .MOTIVE    MAC.NKTO    IGNITION 


densers    for    ignition   apparatus    are   usually    rated 
from  .25  to  .6  of  a  micro-farad  capacity. 

93.  What  is  the  effect  of  too  large  a  condenser  in  a 
magneto? 

Too  large  a  condenser  lowers  the  secondary 
electro-motive  force. 

94.  What  is  the  effect  of  too  small  a  condenser? 

A  condenser  of  low  capacity  results  in  destructive 
arcing  at  the  contact  points  and  a  poor  spark  at 
the  secondary  terminal. 

95.  What  is  a  spark? 

The  luminous  path  produced  by  the  incandescence 
of  the  air  broken  down  by  the  discharge.  The 
space  is  afterwards  filled  with  metallic  vapors, 
given  off  by  the  sparking  electrodes. 

96.  What  is  necessary  to  produce  a  spark? 

In  order  that  a  spark  can  pass  between  two  elec- 
trodes that  are  separated  from  each  other,  there 
must  exist  a  difference  of  electrical  potential  or 
striking  voltage,  the  value  of  which  depends  upon 
the  width  of  the  spark  gap,  the  form  of  the  spark- 
ing electrodes,  the  nature  and  condition  of  the 
medium  in  which  the  spark  passes. 

97.  What  is  a  Spark  plug? 

A  spark  plug  is  a  spark  gap  placed  within  the 
cylinder  of  an  internal  combustion  engine. 


AUTOMOTIVE     MAC.XKTO    IGNITION  47 


97-A.    What  is  meant  by  a  difference  in  potential? 

This  is  a  term  usually  employed  to  denote  the 
voltage  of  the  secondary  current  that  exists  between 
any  two  points  of  the  circuit. 

98.  What  are  the  parts  of  a  spark  plug? 

A  metal  shell  having  a  threaded  end  that  screws 
into  the  cylinder,  a  core  which  must  be  a  good  in- 
sulator and  heat  resisting  is  fitted  pressure  tight 
within  the  metal  shell,  a  metal  rod  through  the 
center  of  the  core  is  fitted  with  a  sparking  electrode 
at  the  end  projecting  into  the  cylinder,  and  a 
terminal  at  the  outer  end  to  which  the  spark  plug 
lead  is  attached.  The  spark  passes  between  the 
center  electrode  and  another  electrode  in  the  shell, 
or  the  spark  may  pass  between  the  center  electrode 
and  the  shell  itself. 

99.  How  is  the  secondary  capacity  of  a  high-tension 

current  distributed? 

The  secondary  capacity  is  -not  situated  at  the 
electrodes  of  a  spark  plug,  it  is  distributed  in  a 
more  or  less  regular  manner  throughout  the  entire 
secondary  circuit. 

100.  What  are  electrodes? 

The  terminals  of  an  electrical  source,  such  as  the 
electrodes  of  a  spark  plug. 

101.  How  should  the  gaps  between  the  spark  plug  elec- 

trodes be  set? 

The   setting  of   the  spark  plug  electrodes  is  an 


48  AUTOMOTIVE    MAGNETO    IGNITION 


important  function  and  it  is  advisable  to  set  the 
gaps  all  alike,  otherwise  the  engine  will  not  run 
evenly,  the  width  of  the  gap  may  vary  under  dif- 
ferent circumstances,  hut  a  setting  of  .025  or  1  40th 
of  an  inch  has  been  found  to  be  good  practice. 

102.     Why   are    the   gaps   of   spark   plug   electrodes   set 
close? 

Although  there  is  but  a  short  distance  between 
the  electrodes  of  a  spark  plug,  the  spark  encounters 
a  certain  resistance  in  overcoming  the  gap,  because 
of  the  compression  of  the  mixture.  The  equivalent 


Cross  section,  spark  plug,  airplane  type. 

spark  at  atmospheric  pressure  may  be  twelve  times 
longer  than  the  spark  under  compression,  which. 
may  be  verified  by  placing  a  spark  gap  in  shunt 
with  the  spark  plug. 

103,     What  is  the  effect  of  too  close  a  gap  of  the  spark 
plug  electrodes? 

Spark  plug  gaps  that  are  set  too  close  tend  to 
heat  the  electrodes  causing  preignition  and  poor  in- 
flammation of  the  mixture. 


AUTOMOTIVE    MAGNETO    IGNITION  49 


104.  What  is  the  effect  of  too  wide  a  gap  of  the  spark 
plug  electrodes? 

Gaps  that  are  too  wide  will  cause  the  engine  to 
miss  when  the  throttle  is  opened  suddenly,  also 
cause  the  magneto  to  spark  at  the  safety  gap. 

105.  What  are  the  usual  causes  of  failure  of  a  spark 
plug? 

Short-circuited  from  carbon,  cracked  porcelains, 
electrodes  burnt  away,  not  pressure  tight,  moisture 
condensing  on  the  insulator. 

106.  What  is  implied  by  the  term  brush  discharge  and 
how  does  it  occur? 

It  is  an  electrical  phenomenon  which  may  be  ob- 
served in  the  dark  in  the  form  of  a  luminous  silent 
discharge  which  occurs  at  the  high-tension  cables 
and  sometimes  the  spark  plugs.  It  is  due  to  the 
nature  of  the  high-tension  current,  a  leakage  oc- 
curring into  the  air.  The  ignition,  however,  is  not 
affected  bv  it. 


107.  How    would    you   locate    a    defective    spark   plug 
cable? 

By  observing  the  leakage  of  the  high-tension  cur- 
rent in  the  dark  or  the  failure  of  the  high-tension 
current  to  reach  the  spark  plug. 

108.  What  is  a  storage  battery? 

Two  inert  plates  immersed  in  a  liquid1  incapable 
of  acting  chemically  on  either  of  the  plates  until 
after  the  passage  of  an  electric  current,  when  they 


50  AUTOMOTIVE    M. \GXKTO    IGXITIoX 


become  capable  of  furnishing  an  independent  elec- 
tric current.  A  storage  battery,  so  called  does  not 
store  electricity,  any  more  than  a  spring  of  a  clock 
can  be  said  to  store  time  or  sound.  The  spring 
stores  muscular  energy,  that  is,  renders  the 
muscular  kinetic  energy,  potential,  which  again  be- 
coming kinetic,  causes  the  works  of  a  clock  to  move 
and  strike.  In  the  same  way  in  a  so-called  storage 
battery,  the  energy  of  an  electric  current  is  caused 
to  produce  electrolytic  decompositions  of  such  a 
nature  as  to  independently  produce  a  current  on  the 
removal  of  the  electrolizing  current. —  (Houston.} 

109.  What  is  the  principle  of  a  storage  battery? 

A  storage  battery  does  not  actually  store  elec- 
tricity, nor  does  it  make  electricity,  it  is  simply  a 
reservoir.  The  term;  charging  a  battery  by  the 
use  of  an  electric  current  brings  about  a  chemical 
change,  which  in  turn  will  produce  electricity  when 
the  circuit  is  completed. 

110.  How  would  you  describe   the   construction   of  a 
storage  battery? 

A  storage  battery  is  composed  of  two  sets  of 
plates  separated  from  each  other  by  strips  of  wood 
called  separators.  Alternate  plates  are  fastened 
together,  one  group  at  one  of  the  upper 
corners,  the  other  group  at  the  opposite  diagonal 
corner.  The  two  groups  of  plates  are  designated. 
respectively,  as  negative  and  positive.  There  is 
usually  one  more  plate  in  the  negative  group.  The 
negative  plates  are  filled  with  spongy  lead  and  the 
positive  plates  with  lead  peroxide.  The  two  groups 


AUTOMOTIVE    MAGNETO    IGNITION  51 


of  plates  are  placed  in  a  jar  made  of  hard  rubber, 
commonly  called  a  cell,  the  plates  rest  on  a  pair  of 
ribs  to  allow  any  of  the  active  material  which  may 
drop  from  the  plates  to  collect  in  the  bottom  of 
the  cell  without  causing  an  internal  short  circuit. 
The  plates  after  being  placed  in  the  cells  are  entirely 
covered  with  a  solution  of  chemically  pure  sulphuric 
acid  and  distilled  water,  this  solution  has  a  specific 
gravity  of  1.275 — 1.300  Baume  scale,  when  the 
battery  is  fully  charged.  This  solution  is  called 
the  electrolyte,  the  electrolyte  of  a  fully  charged 
storage  battery  is  therefore  a  solution  of  two  parts 
concentrated  sulphuric  acid  and  three  parts  water. 

111.  What  happens  within  a  storage  battery  when  it 
is  discharging? 

\Yhen  a  storage  batten*  is  discharging,  the  sulph- 
uric trioxide  of  the  sulphuric  acid  unites  with  the 
active  material  in  both  sets  of  plates,  forming  lead 
sulphate  on  the  plates  and  leaving  water  in  the 
solution,  thus  diluting  it  and  raising  the  proportion 
of  water  to  acid.  For  this  reason  a  storage  battery 
should  be  recharged  at  once  after  being  discharged, 
as  the  forming  of  lead  sulphate  on  the  plates  will 
eventually  ruin  the  battery. 

112.  What  happens  within  a  storage  battery  when  it 

is  being  charged? 

\Yhen  the  storage  battery  is  charged  by  sending 
a  direct  current  of  electricity  through  it  in  the 
opposite  direction  from  which  it  was  delivered  from 
the  battery,  a  reverse  action  takes  place.  The 
sulphuric  trioxide  leaves  the  plates,  thus  doing 


52 


AUTOMOTIVE    MAGNETO    IC.MTIOX 


away  with  the  lead  sulphate  which  Unites  with  the 
water  in  the  solution,  forming  sulphuric  acid  and 
increasing  the  specific  gravity  of  the  electrolyte. 


UNSCREW 

THIS  CAP 


a       Section  of  a  storage  battery  of  the  lead  plate  type. 
113.     How  is  the  capacity  of  a  storage  battery  rated? 

The  amount  of  current  a  storage  battery  will 
store  or  discharge  depends  upon  the  area  of  the 
plates  contained  within  it.  and  usually  measured  in 
ampere  hours.  Thus  a  battery  of  ten  amperes  f»r 
ten  hours  or  five  amperes  for  twenty  hours  or  one 
ampere  for  one  hundred  hours  is  said  to  have  a 
capacity  of  one  hundred  ampere  hours. 


AUTOMOTIVE    MAGNETO    IGNITION  53 


114.  Why  is  it  necessary  to  add  water  to  the  electro- 
lyte in  a  storage  battery? 

Pure  distilled  water  only  should  be  added  to  the 
electrolyte  in  a  storage  battery,  covering  the  plates 
to  a  depth  of  l/&  of  an  inch,  to  make  up  for  the 
loss  of  evaporation,  otherwise  the  capacity  of  the 
battery  will  suffer  and  the  exposed  plates  become 
sulphated,  eventually  ruining  the  battery. 

115.  What  is  the  electro-motive  force  or  voltage  of  a 

storage  battery? 

When  a  storage  battery  is  freshly  charged,  each 
cell  will  be  found  to  have  an  E.M.F.  of  about  2.25 
to  2.50  volts,  but  after  being  used  a  short  time  this 
falls  to  about  2  volts,  at  this  figure  it  remains  until 
the  cell  is  nearly  exhausted.  This  applies  to  the 
lead  plate  type  of  storage  battery. 

116.  What  is  an  Edison  storage  battery  and  how  does 
it  differ  from  the  lead  type  battery? 

This  battery  embodies  a  construction  which  em- 
ploys an  entirely  different  combination  of  elements 
from  that  used  in  the  lead-acid  types.  The  active 
materials  are  nickel  hydrate  and  iron  oxide  and  the 
electrolyte  or  liquid  which  surrounds  the  elements 
is  an  alkaline  solution  of  potassium.  The  positive 
plate  consists  of  perforated  cylindrical  steel  tubes 
containing  nickel  hydrate  and  pure  metallic  nickel 
flake.  The  negative  plate  consists  of  perforated 
flat  steel  pockets  contaning  iron  oxide. 

117.  What  is  the   electro-motive   force   of  an   Edison 
Storage  Battery? 

At  the  beginning  of   discharge  there  is  a  peak 


54 


AUTOMOTIVE    MAGNETO    IGNITION 


voltage  of  short  duration  which  may  he  anywhere 
from  1.3  to  1.5  volts  depending  upon  the  period 
elapsing  between  charge  and  discharge.  Practically 
the  maximum  voltage  during  a  normal  rate  discharge 
is  about  1.3  volts  per  cell.  Open  circuit  voltage 


NE6ATIVE  POLE 
HARD  RU88tR 
9LANO    <., 


SIDE  ROD  IN5ULATC& 


Section  of  a  storage  battery  of  the  Nickel-Iron  type. 

is  variable  and  has  no  useful  significance  in  storage 
battery  practice.  The  Edison  Storage  Battery  will 
maintain  an  average  voltage  of  1.2  volts  during  its 
discharge.  When  the  voltage  drops  to  1  volt  the 
battery  may  be  considered  discharged. 


AUTOMOTIVE    MAGNETO    IGNITION  55 


118.  How  is  the  density  of  the  electrolyte  in  a  storage 
battery  tested? 

It  is  tested  by  means  of  a  hydrometer  which  is 
graduated  to  read  the  density  (specific  gravity) 
on  a  scale  on  the  stem  of  the  hydrometer.  The 
hydrometer  is  usually  enclosed  in  a  glass  tube  which 
holds  a  portion  of  the  liquid  withdrawn  from  cell 
to  be  tested,  the  lower  end  of  the  glass  tube  is 
fitted  with  a  rubber  tube  long  enough  to  reach  the 
liquid  in  the  cell  through  the  filler  cap,  the  upper 
end  of  the  glass  tube  is  fitted  with  a  bulb  syringe. 
When  enough  of  the  liquid  is  withdrawn  from  a 
cell  to  float  the  hydrometer  a  reading  can  be  taken 
at  the  stem  of  the  hydrometer,  rising  above  the 
level  of  the  liquid  within  the  tube. 

119.  What  is  specific  gravity? 

Specific  gravity  is  the  weight  of  a  substance 
compared  with  the  weight  of  the  same  bulk  of 
another  substance.  Water  is  taken  as  the  standard 
for  liquids. 

120.  What  is  meant  by  the  term,  Leads? 

The  insulated  conductors  which  lead  to  and  from 
a  source  of  electricity,  such  as  the  leads  of  a  storage 
battery. 

121.  What  is  meant  by  Sulphating  in  a  Storage  Bat- 
tery? • 

The  formation  of  a  hard  white  basic  sulphate  on 
the  plates  of  a  storage  battery,  due  to  the  battery 
remaining  in  a  discharged  condition. 


56 


AUTOMOTIVE    MAGNETO    IGNITION 


Half  Full 


Charged 


Hydrometer  syringe,  the  hydrometer  will  float  in  the 
electrolyte  of  a  lead  plate  storage  battery  when  it  is  in  a 
discharged,  half  charged  or  charged  state  as  indicated. 


AUTOMOTIVE    MAGNETO    IGNITION  57 


122.  What   is  meant  by   Buckling  of   the   plates   in  a 
storage  battery? 

The  warping  in  storage  battery  plates  due  to  a 
too  rapid  discharge. 

123.  What  methods  are  used  to  find  the  polarity  of  a 
Storage  Battery  or  charging  circuit? 

Dip  the  leads  from  a  storage  battery  or  charging 
circuit  in  a  glass  of  water  with  a  little  salt  in  it, 
bubbles  will  appear  at  the  negative  pole. 

Connect  the  leads  of  a  storage  battery  to  copper 
wires  and  hold  them  on  a  slice  of  raw  potato  about 
a  quarter  of  an  inch  apart,  the  positive  pole  will 
turn  green. 

A  polarity  indicator  connected  in  the  circuit 
of  a  storage  battery  will  show  red  at  the  negative 
pole. 

Procure  some  blue  litmus  paper  from  a  drug 
store,  moisten  the  same,  place  the  two  leads  of  a 
storage  battery  on  the  moisted  paper  about  a  quarter 
inch  apart,  the  positive  pole  will  turn  the  litmus 
paper  red. 

124.     What  is  a  battery  charging  circuit? 

In  a  battery  charging  circuit  a  source  of  direct 
current  is  usually  connected  to  a  fused  double-throw 
switch,  one  of  the  switch  leads  going  to  a  bank 
of  lamps  connected  in  multiple,  the  other  lead 
from  the  lamps  connecting  to  one  of  the  terminals 
of  the  storage  battery  and  the  other  terminal  con- 
nected to  the  knife  switch.  On  a  110  volt  line 
the  battery  will  charge  approximately  at  the 


58  AUTOMOTIVE    MAGNETO    IGXITION 


DATTER.Y 


1 1 1 1 1 


LAMPS 


6 


SWITCH 


10      01 


no  VOLTS 


Wiring  plan     of   a    storage   battery   charging    circuit. 


AUTOMOTIVE    MAGNETO    IGNITION  59 


rate  of  1  ampere  per  hour  for  every  32  C. P.  carbon 
lamp  or  y2  ampere  if  16  C.P.  carbon  lamps  are  used. 
The  positive  lead  of  the  charging  circuit  must  .be 
connected  to  the  positive  terminal  of  the  battery  > 


125.  How  should  a  storage  battery  be  properly  con- 
nected to  a  charging  circuit,  when  the  polarity  of 
neither  the  charging  circuit  or  the  storage  battery 
are  known? 

If  the  leads  of  a  charging  circuit  having  a  lamp  in 
series  with  it  are  connected  to  a  .storage  battery, 
first  one  way,  then  in  the  reverse  way,  it  will  be 
noticed  that  there  is  a  difference  in  the  brightness 
of  the  lamp.  The  battery  is  connected  properly 
whichever  way  the  lamp  glows  dim. 


126.     How  is  a  dry  cell  constructed? 

A  dry  cell  comprises  a  container  of  zinc  which 
forms  one  of  the  electrodes,  the  zinc  container  is 
lined  with  absorbent  or  blotting  paper,  this  is  satu- 
rated with  a  solution  containing  zinc  chloride  and 
sal-ammoniac.  In  the  center  there  is  a  carbon  rod 
or  plate  around  which  is  packed  a  mixture  of, 
maganese  dioxide  (Mn  02)  and  powdered  carbon. 
The  carbon  electrode  is  usually  cappe.d  with  a  brass 
piece  terminating  in  a  binding  post,  another  bind- 
ing post  is  soldered  .to  the  top  of  the  zinc  container j 
The  binding  post  on  the  carbon  is  the  positive  and 
the  binding  post  on  the  zinc  is  the  negative  terminal. 
The  action  of  the  cell  is  as  follows ;  the  manganese 
dioxide  is  a  depolarizer,  it  gives  up  oxygen,  this  com-, 
bines  with  the  hydrogen  gas  which  is  liberated  by  the 


60  AUTOMOTIVE    MAGNETO    IGNITION 


chemical  action  within  the  cell.  The  hydrogen  and 
oxygen  combine  to  form  water,  which  remains  in 
the  cell  and  furnishes  the  moisture  necessary  for 
the  continuous  generating  of  current. 


Dry  batteries  connected  in  multiple-series. 


127.     How   should  a  set  of  dry  batteries  be   connected 
to  insure  long  life  and  service? 

A  dry  cell  is  usually  rated  at  1.25  volts  and  .25 
ampere.  To  obtain  the  best  results,  a  set  of  dry 
batteries  should  be  connected  in  multiple-series,  for 
example,  a  circuit  requiring  6  volts  and  1  ampere, 
20  cells  should  be  used,  connect  5  cells  in  series,  that 
is,  the  positive  terminal  of  one  cell  is  connected  to 
the  negative  terminal  of  the  next  cell  until  5  cells 
are  connected  in  series,  leaving  a  positive  and  nega- 
tive terminal  open,  then  connect  4  such  sets  in 


AUTOMOTIVE    MAGXICTO    IGNITION  61 

multiple,  that  is,  all  of  the  positive  terminals  of 
each  series  are  connected  to  one  lead,  and  all  of  the 
negative  terminal  to  another  lead  as  per  diagram. 

128.  What  is  Electromotive  Force? 

The  force  that  causes  electricity  to  move.  Usually 
abreviated  E.  M.  F. 

129.  What    is    the    estimated    velocity    of    the    electric 
current? 

It  has  been  estimated  that  the  velocity  of  elec- 
tricity through  a  copper  wire  is  288.000  miles  per 
second. 

130.  What  is  the  difference  between  static  and  voltaic 
electricity? 

Static  electricity  is  sudden,  noisy  and  convulsive, 
voltaic  electricity  is  silent,  constant  and  powerful. 

131.  What  is  an  Ampere? 

The  practical  unit  of  the  rate  of  flow  of  electric 
current. 

132.  What  is  an  ampere  Hour? 

Amperes  of  current  flowing  in  an  electrical 
circuit  multiplied  by  time  in  hours,  equals  ampere 
hours. 

133.  What  is  a  Milli-ampere? 

The  1000th  part  of  an  ampere. 


62  At'TOMOTIVK     MAC.XKTO     IC.N  IT1ON 

134.  What  is  an  alternating  current? 

An    electric   current    which    flows    alternately    in 
opposite  directions. 

135.  What  is  direct  current? 

An  electric  current  flowing  in  one  direction. 

136.  What  is  meant  by  the  term,  Positive  pole? 

.In  .a  magnetic  circuit,  the  north  pole  from  which 
the  lines  of  force  emerge  into  the  air.  In  an  elec- 
trical circuit,  the  pole  from  which  the  current  flows 
into  a  circuit. 


Cylinder,  rotary  engine. 

137.  What  is  meant  by  the  term,  Negative  pole? 

In  a  magnetic  circuit,  the  negative  pole  into  which 
the  lines  of  force  flow.  Jn  an  electrical  circuit,  the 
pole  into  which  the  current  flows  after  having  passed 
through  the  circuit  connected  to  the  source. 

138.  What  is  an  electrical  conductor? 

A  conductor  is  a  body  or  substance  which  allows 
the  electric  force  to  pass  freely  through'  it. 


AUTOMOTIVE    MAGNETO    IGNITION  63 


139.  What  is  an  insulator? 

An  insulator  is  a  non-conductor,  offering  con- 
siderable resistance  to  the  flo\v  of  the  electric  cur- 
rent. Rubber  is  one  of  the  best  insulators. 

139- A     Wh£t  is  called  insulation? 

A  non-conducting  covering,  to  prevent  the  leak- 
age of  the  current  in  any  metallic  substance. 

140.  What  is  Resistance? 

That  property  of  an  electrical  conductor  by  which 
it  opposes  the  flow  of  an  electrical  current. 

-141.  -What  is  the  unit  of  electrical  resistance? 

The  unit  of  electrical  resistance  is  called  an  ohm, 
it  is  the  amount  of  resistance  that  will  limit  the 
flow  of  an  electro-motive  force  of  one  volt  to  a 
current  of  one  ampere  in  an  electrical  circuit. 

142.     What  is  Ohms  law  and  how  is  it  applied? 
E 

|||  I=  IT 

The  current  in  amperes  is  equal  to  the  electro- 
motive force  in  volts,  divided  by  the  resistance  in 
ohms. 

E  -  ,  I    X    R 

The  electro  motive  force  in  volts,  is  equal  to  the 
product  of  the  current  in  amperes  and  the  resistance 
in  ohms. 

E 

:!  I       R=~ 

The  resistance  in  ohms  is  equal  to  the  electro- 
motive force  in  volts,  divided  by  the  current  in  am- 
peres . 


64  AUTOMOTIVE    MAGNETO    IGNITION 


143.     What  is  a  Rheostat? 

A  rheostat  is  a  device  for  the  purpose  of  vary- 
ing the  resistance  of  an  electrical  circuit. 


144.  What  is  an  open  circuit? 

An  open  circuit  exists  when  a  continuous  elec- 
trical circuit  is  broken,  preventing  the  flow  of  cur- 
rent through  it. 

145.  What  is  a  closed  circuit? 

An  electrical  circuit  is  closed  when  a  conducting 
continuous  path  is  established  that  a  current  can 
pass. 

146.  What  is  a  short  circuit? 

A  shunt  path  of  low  resistance  around  any 
portion  of  a  circuit,  which  prevents  the  flow  of 
current  through  the  main  circuit. 

146- A.     What  is  meant  by  the  term  ground  circuit? 

The  term  applied  to  the  return  circuit  of  the 
primary  and  secondary  windings  of  a  magneto,  when 
the  current  flows  through  some  metallic  part  of  the 
magneto,  other  than  an  insulated  conductor. 

147.  What  is  an  electrical  capacity? 

The  ability  of  a  conductor  to  permit  a  certain 
quantity  of  current  to  be  passed  into  it  before 
acquiring  a  difference  in  potential. 


AUTOMOTIVE    MAGXETO    IGNITION  65 

148.  What  is  meant  by  dampening? 

The  act  of  bringing  the  pointer  of  an  electric 
measuring  instrument  to  rest  quickly. 

4 

149.  What  is  a  Switch? 

,A  switch  is  a  device  for  opening  or  closing  an 
electrical  circuit. 

149- A.     What  is  an  ignition  switch? 

A  switch  with  one  wire  leading  to  the  ground 
terminal  on  the  magneto,  the  other  wire  from  the 
switch  is  grounded  to  some  metallic  part  on  the 
engine,  when  switch  contacts  are  closed  the  primary 
current  is  grounded  and  the  magneto  becomes  in- 
operative. 

150.  What  are  common  causes  of  failure  in  a  switch? 

Loose  or  dirty  contacts  or  poor  connection  at 
the  terminals. 

151.  What  is  Platinum? 

A  refractory  white  metal  which  does  not  oxidize 
readily,  the  specific  gravity  of  platinum  is  21.53, 
which  means  that  this  metal  is  21.53  times  heavier 
than  water. 

152.  What  is  a  test  line? 

A  test  line  consists  of  a  connection  to  a  110  or 
220  volt  circuit,  preferably  direct  current,  one  of 


66 


AUTOMOTIVE    M.UIXKTO    IGNITION 


the  line  wires  terminating  in  a  flexible  cable  with 
a  piece  of  l/16th  of  an  inch  copper  wire  at  the 
end  for  testing.  The  other  line  wire  is  connected 
to  a  lamp  socket  carrying  a  lamp,  the  other  con- 
nection from  the  socket  terminates  in  another  flex- 
ible cable.  \Yhen  the  ends  of  the  two  flexible  leads 
are  brought  together,  the  circuit  is  completed  and 
the  lamp  lights.  The  test  line  will  be  found  useful 
for  testing  the  continuity  of  windings,  open  or  short 
circuits,  condensers,  etc. 


P>ux/er  test  set. 


153.     What  is  a  buzzer  test  set? 

A  box  containing  two  dry  cells,  on  top  of  which 
is  mounted  an  ordinary  vibrating  buzzer,  tjie  bat- 
teries in  the  box  are  connected  in  series,  one  of  the 
battery  leads  terminating  at  a  binding  post  on  top 
of  tlie  box,  the  other  battery  lead  connects  to  one 


AUTOMOTIVE    MAGNETO    IGNITION  67 


of  the  terminals  of  the  buzzer,  the  other  terminal 
from  the  buzzer  is  connected  to  another  binding 
post  on  top  of  the  box.  A  pair  Of  flexible  leads 
with  spring  clips  at  the  ends  are  useful  for  test- 
ing circuits  in  ignition  wiring,  also  for  setting  the 
magnetic  break  on  magnetos,  etc. 

154.  What    is    an    induction    coil    or    transformer    as 
applied  to  ignition? 

A  coil  wherein  the  electro-motive  force  of  a 
portion  of  a  circuit  is  by  mutual  induction  made  to 
cause  a  higher  electro-motive  force  in  a  contiguous 
circuit  such  as  the  secondary  winding. 

155.  What   are   the   units   of   a   modern    Battery-timer 

.ignition  system? 

(' 

.1  combined  timer-distributor,  a:  transformer  coil, 
a  storage  battery  and  a  generator  to  keep  the  battery 
charged. 


156.     How  does  a   Battery-timer   system  operate? 

When  in  operation,  the  contact  points — which  in 
many  cases  are  composed  of  tungsten — are  first 
closed  by  the  action  of  a  spring  for  a  certain  period 
during  which  the  primary  grows  in  value,  at  the 
proper  time  the  contact  points  are  suddenly  separ- 
ated by  the  action  of  the  cam.  At  that  instant  the 
high-tension  spark  occurs  as  a  result  of  the  enor- 
mous voltage  induced  in  the  secondary  winding  by 
the  collapsing  of  the  magnetic  field  created  by  the 
primary  current.  The  intensity  of  the  high-tension 


68 


AUTOMOTIVE    MAGNETO    IGNITION 


spark  is  dependant — other  things  being  equal— on 
the  value  of  the  primary  current  when  the  contact 
points  are  separated. 


SWITCH 


TO  SPAffff    PLU6S 


RATJERY       ^= 


COIL 


GROUND 


Typical  battery-timer  circuit. 

The  primary  current  flows  from  battery  ground  to  bat- 
tery, to  switch,  to  ballast  resistance,  to  primary  winding, 
to  circuit  breaker,  to  ground. 

Tbe  high-tension  current  flows  from  coil  ground  to  sec- 
ondary winding  in  coil,  to  distributor,  to  spark  plug,  to 
ground. 


AUTOMOTIVK    MAGNKTO    IGNITION  69 


157.  What  are  the  principal  parts  of  a  typical  Battery- 
timer  ignition  system? 

A  battery,  a  switch,  a  transformer  or  induction 
coil,  a  timer  base  upon  which  the  circuit  breaker  and 
condenser  are  mounted,  a  shaft  having  a  number  of 
cam  lobes  equal  to  the  number  of  cylinders  to  be 
fired,  a  distributor  ringer  is  usually  mounted  on  top 
of  the  timer  shaft,  a  cover  which  at  the  same  time 
acts  as  a  distributor  completes  the  outfit. 

158.  What  is  the  usual  arrangement  of  the  timer  parts? 

A  plate  on  which  the  circuit  breaker  and  con- 
denser are  mounted,  a  base  which  forms  a  bearing 
for  the  shaft  which  carries  the  cam  and  distributor 
finger,  the  whole  being  surmounted  by  the  dis- 
tributor. An  extended  arm  is  provided  for  the 
variation  of  the  spark. 

159.  How   are   the   windings   of  a    Battery-timer   con- 
nected? 

The  primary  winding  of  the  transformer  is  con- 
nected in  series  with  the  ballast  resistance  and  the 
circuit  breaker,  a  condenser  is  connected  directly 
across  the  points  of  the  circuit  breaker.  The  second- 
ary winding  is  grounded  at  one  end  and  the  other 
end  leads  to  the  rotating  finger  of  the  distributor. 

160.  What  is  the  ballast  resistance  in  a  Battery-timer 
coil? 

The  small  amount  of  resistance  which  is  connected 
in  series  with  the  primary  winding,  this  limits  the 
amount  of  battery  current  flowing  through  the  coil. 


70  AUTOMOTIVE    M  . \C..\KTO    IGNITION7 


161.  What  is  the  action  of  the  Ballast  resistance? 

When  the  tinier  coil  operates  under  normal  con- 
ditions, the  ballast  resistance  does  not  affect  the 
amount  of  current  flowing  through  the  primary 
winding,  if  the  engine  stops  and  the  switch  is  not 
placed  in  the  "off"  position  to  cut  off  the  flow  of 
battery  current,  under  this  condition  an  increased 
amount  of  current  flows  through  the  primary 
circuit  and  the  ballast  resistance,  with  the  result 
that  the  ballast  resistance  heats  and  offers  a  greater 
resistance  this  limits  the  amount  of  current  flowing 
through  the  primary,  preventing  it  from  burning 
out  from  any  excess  of  battery  current  and  at  the 
same  time  preventing  a  rapid  discharge  of  the 
battery. 

162.  What  is  meant  by  battery-timer  coil  lag? 

Between  the  instant  of  opening  of  the  primary 
circuit  :an.d  the  occurrence. of  the  spark  at  the  spark 
plug,  an  interval  of  time  elapses  which  is  appreciable 
in  comparison  with  the  length  of  time  required 'by 
one  revolution  of  a  high  speed  engine.  A  certain 
amount  of  time  is  required  for  the  primary  current, 
to  attain  its;  full  strength,  this  is  called  the  magnetic. 
lag..fof  the  coil.  The  time  required  for  the  timer 
contacts  to  open  or  close  through  the  action  of  a, 
spring  also  requires  some  time,  this  is  called  the 
mechanicaj  lag  of  the  circuit,  breaker.  . 

163.  What  is  the  effect  of  lag  in  a  battery-timer  system? 

In  a  battery-timer  system  the  spark  must  be: 
advanced  because  the  spark  does  not  •  take <  place 


AUTOMOTIVE    MAGNETO   IGNITION  71 


at  the  moment  when  the  contact  points  open,  there 
is  a  retarding-  influence  that  varies  according  to 
circumstances,  that  is  one  reason  why  a  battery- 
timer  requires  more  advance  than  a  magneto. 


163-A  If  the  lag  in  a  battery-timer  system  on  an  en- 
gine running  at  2000  R.P.M.  was  equal  to  1/30 
of  a  revolution  measured  on  the  flywheel,  how 
far  must  the  timing  lever  be  advanced  to  correct 
it? 
30  divided  by  360  equal  12.  timer  running  at  cam 

shaft  speed,  advance  necessary  6  degrees. 


164.  What  is  the  difference  between  a  timer  coil  and 
the  winding  of  a  high-tension  magneto? 

If  the  ballast  resistance  were  eliminated  so  that 
the  primary  winding  is  short-circuited  upon  itself 
when  the  contacts  are  closed,  the  only  vital  dif- 
ference between  the  working  of' the  two  systems  is 
that,  \vhereas.  in  the  action  of  the  magneto,  the 
primary  current  is  generated  by  magnetic  induction 
and  in  a  battery-timer  system  the  current  is  supplied 
by  a  battery  of  practical  constant  voltage. 

165.  What  is  the  principle  of  ignition  of  the  mixture 
in  an  engine? 

The  principle  of  ignition  of  the.. mixture  in  an 
internal  combustion  engine  may  be  .defined  as  ! fol- 
lows, to  produce  at  a  precise  moment  in  the.  travel 
of  the  piston,  a  spark  capable  of  igniting  the  mixi-r. 
ture,  the  moment  when  the  spark  should  take  place 
varies  with  the  engine  and  its  speed,  -  ; 


72  AUTOMOTIVE    MACM-TO    ir.NITlON 


The  ignition  of  the  mixture  is  not  instantaneous, 
the  spark  first  ignites  the  mixture  immediately  sur- 
rounding the  electrodes  of  the  spark  plug,  the  pro- 
pogation  of  the  flame  takes  place  at  a  speed  <> 
about  12  feet  per  second,  so  in  order  to  obtain  the 
maximum  effect  on  the  piston,  the  spark  should 
take  place  at  a  given  time  before  the  passing  of  the 
crank  over  the  top  dead  center. 


Flame  propagation  around  the  electrodes  of  a  spark  plug'. 

166.     What  is  the  principle  of  compression  in  internal 
combustion  engines? 

One  of  the  fundamental  principles  of  the  internal 
combustion  engine  is  the  compression  of  the  charge, 
of  course  the  gas  or  mixture  would  explode  at 
atmospheric  pressure,  but  it  was  discovered  long 
ago  that  the  explosion  was  much  stronger  if  com- 
pression took  place  before  ignition. 


AUTOMOTIVE    MAC.NKTO    IGX1TTOX 


When  the  mixture  is  compressed  to  half  of  its 
original  volume  the  pressure  is  doubled,  when  the 
piston  begins  to  return  on  the  compression  stroke 
the  inlet  valve  closes,  forcing  the  mixture  into  a 
smaller  space,  one  quarter  of  its  original  volume  as 
a  rule.  Then,  when  ignited,  it  explodes  with  far 
greater  force  than  otherwise  could  be  possible,  in 
this  way  by  using  a  smaller  engine  cylinder  and  less 
combustible  mixture,  higher  efficiency  is  obtained. 
When  an  engine  runs  at  high  speed,  the  mixture 
cannot  enter  fast  enough  to  fill  the  cylinder  before 
the  inlet  valve  closes,  and  for  this  reason  some 
engines  have  more  than  one  inlet  valve  or  the  inlet 
valve  is  not  closed  until  the  piston  has  passed 
the  lower  dead  center. 

As  a  rule  the  mixture  has  to  rush  through  the 
carburetor  and  along  the  induction  pipe  and  finally 
through  the  inlet  valve  and  several  short  turns. 
On  occasions  the  speed  of  the  mixture  is  apt  to  be 
more  than  1000  linear  feet  per  minute,  but  owing 
to  friction  a  full  charge  of  gas  is  unable  to  enter 
the  cylinder  in  the  very  short  period  the  inlet  valve 
is  open,  so  the  compression  suffers,  the  same  thing 
happens  when  the  engine  is  very  hot,  as  the  high 
temperature  rarifies  the  charge,  making  it  less 
powerful,  and  consequently  great  care  is  taken  to 
design  the  induction  passage  correctly  in  order  that 
full  compression  and  the  greatest  efficiency  may 
be  obtained.  High  compression  also  has  its  effect 
on  the  ignition  which  manifests  itself  in  that  suffi- 
cient spark  may  be  obtained  from  the  ignition 
system  under  normal  compression,  but  when  the 
compression  is  exceedingly  high,  the  spark  is  apt 
to  take  the  safety  gap  or  fail  altogether. 


74 


AUTOMOTIVE     M  ACN  KTf)    IGNITION 


167.     How  would  you  define  the  term  Cycle  as  applied 
to   the   internal   combustion   engines? 

A  scries  that  repeats  itself,  a  recurring  series  of 
operations,  as  in  internal  combustion  engines1  in 
which  heat  is  imparted  or  taken  from  a  substance, 
which  by  expansion  gives  out  energy,  and  is  finally 
returned  to  its  original  condition. 


Angularity   of   the   cylinders    of   a   90  degree   Vee   type 
engine. 

168.     What  is  meant  by  a  cycle   as  applied  to  the  in- 
ternal combustion  engine? 

The  four  strokes  necessary  for  one  operation. 


169.     Name  in  detail  the  operation  of  the  four  stroke 
cycle  internal  combustion  engine? 

With  the  intake  valve  open  the  piston  descends 
and  draws  in  the  mixture  on  the  suction  stroke, 
then  the  piston  rises,  with  the  valves  closed,  com- 
pressing the  mixture  on  the  compression  stroke. 
When  the  piston  passes  over  dead  center  the  spark 
occurs,  exploding  the  compressed  mixture  and  the 


ATTOMOTIVE    MAGNETO    IGNITION  /O 


piston  is  driven  down  with  the  valves  still  closed, 
on  the  power  stroke.  The  piston  again  ascends, 
forcing  the  spent  gases  out  through  the  open  ex- 
haust valve,  completing  the  four  stroke  cycle  with 
the  exhaust  stroke. 


170.  What  is  a  carburetor? 

A  mechanical  device  for  mixing  gasoline  and  air 
in  proper  proportions. 

171.  What  are  the  principal  parts  of  a  carburetor? 

Float  chamber,  spray  nozzle,  air  intake  and 
throttle. 

172.  What  are  the  indications  of  too  rich  a  mixture? 

Black  smoke  issuing  from  the  exhaust. 

173.  What  are  the  indications  of  too  lean  a  mixture? 
Popping  back  into  the  carburetor. 

174.  How  is  the  term  horse  power  defined? 

Horse  power  is  a  term  employed  to  measure 
power,  which  is  the  product  of  force,  acting  through 
a  certain  distance  of  space  and  a  certain  length  of 
time.  1  horse  power  is  equivalent  to  the  force  re- 
quired to  lift  33000  Ibs.  1  foot  high  in  1  minute. 
It  is  the  standard  of  measurements  in  which  all  the 
elements  of  force,  space  and  time  enter.  Horse 
power  as  applied  to  the  gasoline  engine  may  be 


76 


AUTOMOTIVE    MAGXKTO    ir.MTlON 


termed,  brake  or  rated.  Actual  or  brake  horse 
power  is  usually  determined  by  the  use  of  the 
dynamometer,  which  is  a  means  of  converting  the 
power  developed  by  a  gasoline  engine  into  elecricity. 
the  amount  of  electricity  generated  is  measured  in 
volts  and  ampers,  which,  when  multiplied  together 
are  called  watts,  746  watts  equal  1  horse  power, 
therefore  the  number  of  watts,  divided  by  746  would 


Angularity  of  the  cylinders  in  a  45  degree  Vee  type 
engine. 

represent  the  horse  power  developed  by  the  gasoline 
engine  under  test.  Rated  horse  power  is  determined 
by  a  means  of  a  formula  devised  by  the  Society  of 
Automotive  Engineers.  This  formula  is  expressed 
as  follows,  D2  multiplied  by  N,  divided  by  2.5 
equals  horse  power.  In  this  formula  D  equals  the 
bore  of  the  cylinders  in  inches  squared,  and  N  the 
number  of  cylinders  divided  by  the  constant  2  5. 

D2  X  N  =  H.P. 

This  formula,  however,  is  subject  to  modifica- 
tions, as  neither  the  factors  of  piston  speed  or  the 
mean  effective  pressure  are  compensated  for. 


AUTO  MOT  [VE    MAGNETO    IGNITION  77 


It  requires  1  horse  power  to  lift  33000  Ibs.  1 
foot  high  in  1  minute,  or  550  Ibs.  1  foot  high  in 
1  second  or  330  Ibs.,  100  feet  high  in  1  minute. 

175.  How    can    brake    horse    power    be    calculated    by 
formula? 

Pi 

D*  X  -       X   S     X  N 
4 

-X   R.P.M. 
7500 

I)1'      =  Diameter  of  piston,  in  inches  squared. 
Pi 

=  l/4  of  Pi  or  .7854. 
4 

S  =  =  Lenth  of  stroke  in  inches. 
.  N  =--  Number  of  cylinders. 
7500  ==  Constant. 
R.P.M.  ==  Revolutions  per  minute. 

176.  Why  is  it  necessary  to  time  the  magneto  to  the 
engine? 

To  have  the  spark  occur  at  the  proper  moment. 

177.  How  would  you  proceed  to  time  a  magneto  to  an 
engine? 

One  of  the  cylinders  is  usually  designated  as 
No.  1.*  In  an  engine  with  the  cylinders  in  line, 
the  cylinder  nearest  to  the  starting  crank  and  in 
airplane  engines  the  left  hand  cylinders  nearest  to 
the  pump  are  designated  as  No.  1. 

*NOTE— No  standard  designation  of  No.  1  cylinder 
having  been  adopted  by  Airplane  engine  manufacturers, 
all  firing  diagrams  show  No.  1  cylinder  at  the  left  side, 
pump  end. 


AUTOMOTIVE    MAGNETO    IGNITION 


Place  the  piston  of  No.  1  cylinder  on  the  upper 
dead  center  (or  follow  the  manufacturers  instruc- 
tions), place  the  magneto  on  its  base  with  the  coup- 
ling loose,  place  the  timing  lever  in  the  full  re- 
tarded position,  or,  if  the  magneto  is  of  the  fixed 
spark  type  it  must  be  set  a  number  of  degrees  later 
when  timing  in  order  to  prevent  any  back-kick  from 
the  engine. 


-o 


-o 


T 


Magneto  ignition  system,  8  cylinder  Vee  engine,  the 
units  comprise  two  high-tension  magnetos,  firing  one  spark 
plug  in  each  cylinder  on  separate  engine  blocks. 

RemOve  the  breaker  cover  and  turn  the  magneto 
shaft  in  the  direction  in  which  it  is  to  rotate  until 
the  platinum  points  of  the  circuit  breaker  are  about 
to  separate,  in  this  position  secure  the  coupling  to 
the  magneto  shaft,  taking  care  not  to  alter  the  posi- 
tion of  the  shaft. 

Fasten  the  magneto  to  its  base.  Remove  the 
distributor  block  and  note  which  terminal  of  the 
distributor  block  is  in  contact  with  the  distributor, 
connect  cable  leading  from  the  spark  plug  of  No.  1 
cvlinder  to  the  terminal  on  the  distributor  block 


AUTOMOTIVE    MAGNETO    IGNITION  79 


which  is  in  line  with  the  distributor  brush  or  seg- 
ment and  connect  the  remaining  spark  plug  cables 
according  to  the  sequence  of  firing  and  the  rotation 
of  the  distributor.  If  the  distributor  block  is 
marked  set  the  brush  or  segment  leading  to  No.  1 
terminal  on  the  block  before  securing  the  coupling 
to  the  magneto  shaft. 

178.     What  is  meant  by  timing  lever  manipulation? 

Varying  the  time  of  ignition  is  desirable  for  sev- 
eral reasons  which  may  be  due,  either  to  lag  of  the 
ignition  device,  quality  of  the  mixture,  speed  of  the 
engine  or  conditions  of  load  under  which  the  engine 
is  operated. 

In  a  magneto  a  very  brief  period  of  time  is  re- 
quired to  complete  a  cycle  of  operation  which  con- 
sists of  the  reversal  of  polarity  in  the  windings, 
building  up  and  interrupting-  the  current  in  the 
primary  circuit  and  distributing  the  high-tension 
current  to  the  spark  plugs. 

In  a  battery  ignition  system  more  time  is  required 
to  build  up  the  primary  circuit,  there  may  also  be 
some  mechanical  lag  in  the  interrupter,  consequently 
more  spark  advance  is  necessary  in  a  battery  igni- 
tion system  than  when  magneto  ignition  is  em- 
ployed. 

A  lean  mixture  is  slow  burning,  more  time  be- 
ing required  for  full  inflamation,  the  same  being 
true  of  too  rich  a  mixture,  in  both  cases  the  spark 
timing  must  be  advanced. 

The  lag  of  the  spark  is  proportional  to  the  speed 
of  the  engine,  at  2000  revolutions  per  minute,  the 
crankshaft  will  move  twice  as  far  before  the  spark 


80  AUTOMOTIVE    M. \G.\KTO    rCXITION" 


Valve  and  ignition  timing  of  an  airplane  engine. 

Inlet  valve  opens — dead  center. 

Inlet  valve  closes — 50  degrees  late. 

Ignition  occurs — 20  degrees  ahead  of  dead  center. 

Exhaust  valve  opens — 45  degrees  from  bottom  dead  center. 

Exhaust  valve  closes — 10  degrees  after  top  dead  center 

( FT ispano- Suiza) . 


AUTOMOTIVE    MAGNETO    IGNITION  81 


occurs  than  at  1000  revolutions  per  minute  con- 
sequently an  earlier  spark  timing  is  required. 

The  higher  the  piston  speed  the  earlier  in  the 
•stroke  should  the  spark  occur  in  order  that  the  max- 
imum pressure  may  be  exerted  at  the  most  ad- 
vantageous point.  Consequently  spark  advance  is 
needed  because  after  the  electrical  circuit  is  broken 
and  the  spark  has  taken  place  in  the  combustion 
chamber,  a  short  time  interval  elapses  before  the 
charge  is  fully  ignited  and  sufficiently  expanded  to 
exert  the  maximum  pressure  on  the  piston. 

The  timing  lever  should  be  in  a  position  in  pro- 
portion to  the  load  and  a  good  operator  learns  to 
observe  the  effect  of  manipulating  the  timing  lever 
and  act  accordingly,  gauging  the  lever  position  for 
engine  speed  and  gradually  retard  the  spark  when 
the  engine  is  slowed  down  by  work,  always  just 
keeping  ahead  of  the  knock.  If  the  engine  speed  de- 
creases, either  from  closing  the  throttle  or  excessive 
work,  the  spark  must  be  retarded  or  the  engine  will 
pound  or  knock,  as  the  explosions  tend  to  force 
the  pistons  and  crank-shaft  in  the  wrong  direction. 

179.  What  is  meant  by  the  range  of  advance  and  re- 
tard? 

The  number  of  degrees  advance  or  retard  effective 
on  an  engine  depends  on  the  range  or  movement  of 
the  timing  lever  and  the  relation  of  magneto  speed 
to  engine  speed. 

180.  A  magneto,  driven  at   ^  engine   speed  having  a 
range  of  25  degrees  of  the  timing  lever,  how  many 
degrees  effective  on  the  engine? 

50  degrees. 


82- 


AUTOMOTIVE    MAGNETO    IGNITION 


181.  A  magneto  driven  at  engine  speed,  having  a  range 
of  30  degrees  of  the  timing  lever,  how  many  de- 
grees effective  on  the   engine? 

30  degrees. 

182.  A  magneto  driven  at  1^2  times  engine  speed,  hav- 
ing a  range  of  40  degrees  of  the  timing  lever,  how 
many  degrees  effective  on  the  engine? 

26.66  degrees. 


— o      o— 

-O 


w          w 

r—  O        O—  | 

r-0              0-1 

rO          O- 

Magneto  ignition  system,  8  cylinder  Vee  engine,  the 
units  comprise  'two  high-tension  magnetos,  each  one  firing 
two  spark  plugs  in  each  cylinder  on  separate  engine  blocks. 

183.     What  is  the  relation  of  spark  advance  to  piston 
travel? 

To  ascertain  the  relation  of  spark  advance  in 
degrees  to  piston  travel  in  inches,  it  may  be  cal- 
culated by  means  of  the  accompanying  chart,  in 
which  the  horizontal  lines  represent  the  piston  travel 
in  fractions  of  an  inch  and  the  vertical  lines  the 


AUTOMOTIVE    MAGNETO    IGNITION  83 


stroke  in  fractions  of  an  inch.  It  is  arranged  for 
engines  having  strokes  from  3  to  8  inches,  the  ratio 
between  the  crank  and  connecting  rod  length  being 
1  to  4.5. 

To  find  the  piston  travel  for  an  advance  of. 
30  degrees  in  an  engine  having  a  stroke  of  6  inches, 
the  vertical  line  (7,  is  traced,  upward  until  it  inter- 
sects the  diagonal  line  designating  30  degrees  at  r, 
following  this  to  the  left  it  will  be  noticed  that  the 
intersecting  point  is  just  below  the  y2  inch  division 
line,  or  approximately  .46  of  an  inch.  An  engine 
with  a  stroke  of  6  inches  running  at  1800  r.p.m., 
its  piston  would  be  traveling  1800  feet  per  minute 
(i.  e.  stroke  doubled  or  1  foot  per  revolution), 
30  feet,  or  360  inches  per  second,  so  that  each  inch 
or  the  stroke  would  be  covered  at  an  average  speed 
of  1  inch  in  1/360  of  a  second,  and  the  ^  inch  in 
1  720  of  a  second,  from  which  it  will  be  seen  that 
spark  advance  is  necessary. 


184.     What   effect   would   a    small   amount   of   lag   in  a 
magneto    have? 

In  an  armature  type  of  magneto  sparking  a  six 
cylinder  four  stroke  cycle  engine,  running  at  a  speed 
of  1800  R.P.M.,  when  the  speed  of  the  engine  is 
1200  R.P.M.,  the  current  must  rise  from  zero  to 
its  maximum  value  and  drop  back  to  zero  again 
3600  times  per  minute  or  60  times  per  second.  The 
current  has  l/60th  part  of  a  second  to  rise  to  its 
maximum  and  drop  back  again.  A  lag  of  1/1 200th 
part  of  a  second  corresponds  to  l/40th  of  a  revolu- 
tion or  9  degrees  of  crank  travel. 


84  AUTOMOTIVE    MAGNETO    IGNITION 


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AUTOMOTIVE    MAGNETO    IGNITION 


85 


185.     What  is  the  relation  of  magneto  speed  to  engine 
speed? 

The  relation  of  magneto  speed  to  engine  speed 
is  proportional  to  the  number  of  sparks  required 
per  revolution  of  a  four  stroke  cycle  engine. 


Magneto 
Speed  in 

Cylinders 

Magneto  sparks 
per  360  degrees 

relation 
to  engine 

. 

speed 

1 

1 

V* 

2 

2,    distributor 

l/2 

on  collector 

spool 

2 

1,  distributor                      engine 

spaced  180 

speed 

degrees 

3 

1 

1  l/2 

4 

2 

engine 

speed 

6 

2 

1  1/> 

8 

? 

2 

8 

4 

engine 

speed 

12 

2 

3 

12 

4 

\y2 

12 

6 

engine 

speed 

186.     What   is   the    relation   of    speed    of    the   magneto 
shaft  to  the  distributor  shaft? 

A  four  cylinder  magneto  2  to  1.  A  six  cylinder 
magneto  3  to  1.  An  eight  cylinder  magneto  pro- 
ducing four  sparks  per  revolution  2  to  1.  An  eight 
cylinder  magneto  producing  two  sparks  per  revolu- 
tion 4  to  1.  A  twelve  cylinder  magneto  producing 
four  sparks  per  revolution  3  to  1. 


86  AUTOMOTIVE    'MAGNETO    IGNITION 

•187.     How  would  you  detect  the  failure  of  the  ignition? 
There  would  be  no  spark  at  the  spark  plugs. 

188.  What   would   cause    a    magneto    to    spark   at   the 
safety    gap,    when    the    high-tension    circuit    is   in 
good  order? 

Sparking  at  the  safety  gap  is  an  indication  that 
there  is  a  gap  in  the  secondary  circuit  greater  than 
the  resistance  of  the  secondary  winding,  as  for  in- 
stance spark  plug  electrodes  burning  too. far  apart. 

189.  What  is  a  safety  gap? 

An  auxiliary  path  of  the  high-tension  current  to 
protect  the  winding,  and  insulating  parts  of  the 
magneto,  when  the  high-tension  current  cannot  dis- 
charge itself  through  the  spark  plug  gap,  as  for 
instance  if  a  spark  plug  cable  became  disconnected. 


190.  When  an  engine  will  not  start  but  fires  once  or 
twice  and  then  stops,  the  flywheel  rocking  back 
and  forth,  what  is  the  cause? 

Some  of  the  spark  plug  leads  have  been  mis- 
placed, so  that  after  one  or  two  explosions,  the  next 
one  takes  place  out  of  sequence. 


191.     How  would  you  test  for  trouble  in  a  high-tension 
magneto  ignition  system? 

See  that  the  magneto  ground  or  short-circuiting 
switch  and  wiring  are  in  good  order,  see  that  the 
platinum  contact  points  of  the  circuit  breaker  are 
breaking  properly  and  at  the  correct  time,  if  the 


-AUTOMOTIVE    MAGXKTO    IGNITION  87 


..points  .flash,  .a -defective  condenser  ;or  oil  on  the 
points  may  be  suspected,  see  that  the  distributor 
brushes  are  not  broken  and  in  good  contact  on  the 
segment,  see  that  the  cables  leading  to  the  spark 
plugs  are  not  grounded,  chafed  or  cut.  see  that  the 
spark  plugs  are  in  good  condition. 


192.  What  is  pre-ignition? 

Pre-ignition  is  the  result  that,  in  the  combustion 
chamber,  a  particle  of  carbon  or  some  projection 
inside  of  it  has  become  overheated,  permitting  a  too 
early  ignition  of  the  compression  of  the  gaseous 
mixture. 

193.  What  is  necessary  to  keep  the  magneto  in  good 
running  condition? 

Lubricate  it  at  proper  intervals,  keep  it  clean, 
especially  the  platinum  contact  points  and  dis- 
tributor, also  keep  it  dry.  This  is  about  all  anyone 
should  do,  unless  a  skilled  mechanic,  it  is  unwise 
to  tamper  with  the  instrument  in  case  of  trouble, 
send  it  to  a  service  station. 


194.     How  often  should  a  magneto  be  oiled? 

The  importance  of  oiling  depends  entirely  upon 
the  service  required  from  a  magneto,  on  auto- 
mobiles, every  "1000  miles,  on  motor  trucks,  every 
50  hours  of  operation,  on  airplanes,  every  25  hours 
of  operation  is  a  good  rule. 


88 


AUTOMOTIVE    MAGNETO    IGNITION 


195.     What  arc  the  advantages  of  an  Auxiliary  vibrating: 
system? 

To  assist  the   starting  of   hand  cranked   engines' 
in  cold  weather. 


Magneto    ignition    system.'  8    cylinder    Vee    engine,    the 
units  comprise  two  high-tension  magnetos,  cross-connected, 

firing  two  spark  plugs  in  each  cylinder. 


196.     What  does  an  auxiliary  vibrator  system  consist  of 
and  how  does  it  operate? 

The  auxiliary  vibrator  system  consists  of  a  vib- 
rator, two  small  windings  and  a  condenser,  all 
housed  within  the  switching  device.  The  battery 
current  is  carried  through  the  vibrator  to  the  circuit 


AUTOMOTIVE    MAGNETO    IGNITION  89 


breaker  of  the  magneto;  the  high-tension  current 
being  distributed  to  the  spark  plugs  through  the 
distributor  on  the  magneto.  When  the  switch  lever 
is  placed  on  the  battery  position,  the  current  from 
the  battery  is  conducted  through  the  vibrator  wind- 
ings to  the  vibrator  and  to  the  primary  winding 
of  the  magneto.  The  vibrator  is  simultaneously  set 
into  operation  with  throwing  the  switch  lever 
on  battery,  but  no  sparks  are  produced  at  the  plugs 
until  the  cam  separates  the  platinum  points,  thereby 
bringing  the  magneto  primary  winding  into  the 
circuit.  A  continuous  shower  of  sparks  is  pro- 
duced in  that  period  of  time  in  which  the  platinum 
points  are  held  open  by  the  cam. 

197.     What  are  the  characteristics  of  a  rotary  engine? 

The  steady  running  of  a  rotary  engine  is  due 
to  the  fact  that  there  are  literally  no  reciprocating 
parts  in  the  absolute  sense,  the  apparent  reciproca- 
tion between  the  pistons  and  cylinders  being  solely  a 
relative  reciprocation,  since  both  travel  in  a  circular 
path. 

The  master  rod  in  a  rotary  engine,  is  the  con- 
necting rod  that  is  vertical  when  the  crankshaft  is 
in  a  vertical  position. 

A  seven  cylinder  rotary  engine  has  power  im- 
pulses spaced  102.8  degrees  apart  and  requires  a 
magneto  giving  two  sparks  per  revolution,  driven  at 
\Y\  times  engine  speed. 

The  firing  order  of  a  seven  cylinder  rotary  engine 
is  as  follows ; 

A  nine  cylinder  rotary  engine  has  power  impulses 


90  AUTOMOTIVE    MAC.NKTO    IGNITION 


spaced  80  degrees  apart  and  requires  a  magneto 
giving  two  sparks  per  revolution,  driven  at  2% 
times  engine  speed. 

The  firing  order  of  a  nine  cylinder  rotary  engine 
is  as  follows ; 

1  —3—5—7—9—2—4—6—8. 


Magneto  for  a  9  cylinder  rotary  engine,  the  high-tension 
lead  terminates  in  a  brush-holder,  the  brush  of  which  is 
in  contact  with  the  segments  of  a  separate  distributor. 


The  magneto  is  usually  gear  driven,  the  high- 
tension  lead  terminates  in  a  brush  holder,  the  carbon 
brush  being  in  contact  with  a  separate  distributor 
revolving  with  the  engine,  solid  brass  wires  leading 
to  the  spark  plugs. 


AUTOMOTIVE    MAGNETO    IGNITION  91 


198.  What  is  the  relation  of  magneto  speed  to  engine 
speed  on  a  9  cylinder  rotary  engine,  the  magneto 
giving  two  sparks  per  revolution? 

Ill  a  9  cylinder  rotary  engine  the  power  impulses 
are  spaced,  720  degrees  divided  by  9  or  80  degrees 
apart,  consequently  a  spark  is  required  every  80 


Distributor  of  a  9  cylinder  rotary  engine,  it  rotates  with 
the  engine,  the  distributor  segments  being  connected  to 
the  spark  plugs  with  bare  brass  wires. 


degrees,  with  a  magneto  giving  a  spark  every  180 
degrees,  it  follows  that,  80  divided  by  180  equals 
magneto  speed,  therefore  the  magneto  imust  be 
driven  2^J  times  engine  speed. 


92 


AUTOMOTIVE    MAGNETO    IGNITION 


9  cylinder  rotary  engine,  outline  of  relative  positions  of 
pistons  and  connecting  rods.  No.  1  cylinder  about  to  fire, 
master  rod  in  the  vertical  position. 


AUTOMOTIVE    MAGNETO    IGNITION  93 


Battery  timer  ignition  system,  8  cylinder  Vee  engine,  the 
units  comprise  a  generator,  storage  battery,  two  circuit 
breakers,  two  cross-connected  distributors,  firing  two  spark 
plugs  in  each  cylinder. 


94  AUTOMOTIVE    M.\<;\KT()    K'.MTIOX 


Firing  order  Hispano-Suiza  8  cylinder  Vee  engine. 
viewed  from  pump  end:  1L— 8R— 2L— 7R— 4L— 5R— 3L- 
6R. 

Manufacturer's  firing  order  from  propeller  end:  4L — 
5R_3L— 6R-.1  L— 8R— 2L— 7R. 


AUTOMOTIVE    MAGXKTO    IGXITIOX  95 


Firing  order  Curtiss  8  cylinder  Yee  engine  OX2 
5  R— 2L— 6R— 4L— 8R— 3  L— 7R. 


96  AUTOMOTIVE    MAGNETO    IGNITION 


4 


3K\\/y7 


/ 


I-'iring  order,   Sturtevant  8  cylinder  Vee  enuine 
1 L— 8R— 3L— 6R— 4L— 5R— 2L— 7R. 


INDEX 


Advance  and  retard,  range  of,  179 

Ampere,  131 

hour,  132 

mill!-.  133 

turn,  69 

turn  as  applied  to  a  winding  70 

Atoms,  molecules  and,  10 

Auxiliary  vibrator  system,  advantages  of  an,   195 

construction  and  operation  of 
an,  196 

Battery-timer  coil,  ballast  resistance  in  a,  160 
connections  of  a,  159 
effect  of  lag  in  a,  163 
lag,  162 

Battery-timer  system,  lag  on  an  engine,_163-A 
operation  of  a,  156 
principle  parts  of  a,  157 
units  of  a  modern,  155 

Brush  discharge,  effect  of  a,  106 

Carburetor,  principle  parts  of  a,  171 
what  is  a,  170 

Circuit  breaker,  29 

how  a,  operates,  30 

97 


98  INDEX 


Circuit,  closed,  145 

description  of  a  battery  charging,  124 
distribution    of    the    secondary    capacity    of    a 

high-tension,  99 
effect  of   rapid   breaking  of  the    primary  upon 

the  secondary,  31 
ground,  146-A 

how  to  find  the  polarity  of  a  charging,  123 
open,  144 
proper  method  of  connecting  a  storage  battery 

to  a  charging,   when  the  polarity  of  both  is 

unknown,   125 
short,  146 


Coil,  battery-timer,   159,   160,   164 

induction,  or  transformer.   154 
principle  of  a  reactance,  82 

Condenser,  action  on  primary  winding,  89- A 
construction  of  a.  86 
dielectric  of  a,  87 
discharge,  89 

effect  of  a,  when  the  capacity  is  too  high,  93 
effect  of  a,  when  the  capacity  is  too  low,  94 
how  to  test  a,  91 
functions  of  a.  85 
measuring  the  capacity  of  a,  90 
parts  of  a.  retaining  the  charge,  88 
what  is  a,  84 

Current,  alternating,  134 

definition  of  primary,  71- A 

definition  of  secondary,  71-B 

difference  in  potential  of  the  secondary,  97-A 

direct,  135 

effect  of  the  secondary,  on  the  iron  core,  72 

magnetizing,  65 

secondary  flow  of,  in  a  magneto,  28-C 

velocity  of  the  electric,  129 

Currents,  eddy;  76 

Cycle,  application  of  the   term,    168 
definition  of  the  term,  167 

Dampening,  148 
Distributor,  32 


INDKX  99 


Dry  cells,  connecting  a  set  of.  127 
construction   of  a,   126 

Electrical   capacity.  147 

conductor.    138 
resistance,  unit  of.  141 

Electricity,  difference  between  static  and  voltaic.  130 
theory  of,  9 

Electrodes  of  an  electrical  source,  100 

Electro-magnet,  how    to    determine    the    north    pole    of 

an.  62 
what  is  an,  63 

Electro-motive  force,   12<S 

of  an  Hdison  Storage  Battery,  117 
of  a  lead  plate  storage  battery,  115 
Energy,  6 

kinetic.  8 
potential.   7 


Engine,  characteristics  of  rotary.  197 

how  a  magneto  is  timed  to  an,  177 

lag  of  a  batttery  timer  system,  163-A 

necessity  of  timing  the  magneto  to  an,  176 

nine  cylinder  rotary,  198 

operation  of  a  four  stroke  cycle,  169 

principle  of  compression  in  an,   166 

principle  of  ignition  in  an,  165 

relation  of,  speed  to  magneto  speed,  185 

speed,  timing  range  on  a  magneto,  180,  181,  182 


Horse  power  defined,  174 

formula  for  brake,  175 


Ignition,  advantages  of  electricity  in  producing.  5 
definition  of  the  term.  1 
effect  of  failure  of,  187 
evolution  of.  3 
how,  is  produced,  2 
parts  of  a  high-tension  system  of,  36 
pre-,  192 

principle  of  magneto,  20 
principle  of.  in  an  engine,  165 


100  INDEX 

IGNITION — co  n  tin  ued 

source  of  energy  that  will  produce.  4 
systems  of,  in  use  at  the  present  time,  38 
switch,  149-A 
testing  for   trouble    in   a   high-tension    system 

of,  191 

what  is  dual,  33 
what  is  duplex,  34 
what  is  independent.  35 

Induction,  power  of  magnetic,  56 
principle  of  electric,  71 

Insulation,  139- A 
Insulator,  139 


Iron  core,   effect  of  duration  of  the  secondary  spark  on 

the,  73 

effect  of  the  secondar\r  current  on  the,  72 
hysterisis  effect  on  an,  78 
used  in  a  winding,  why  is  an.  70-B 

Laminae,   what  are,  75 

Magnet,  coercive  force  of,  49-A 

how  to  determine  the  north   pole  of  a,  61 
how   to  determine   the   north   pole   of  an   elec- 
tro-. 62 

keeper  of  a,  53 

proper  way  to  insert,  in  magnetizing  coil,  66-A 
super-saturation  of  a.  51 
what  is  a,  42 
what  is  a  bar.  44 
what  is  a  bell   shaped.  48 
what  is  a  compound.  47 
what  is  a  horse-shoe,  46 
what  is  a  permanent,  45 
what  is  an  electro-,  63 


Magnets,  retaining  the  strength  of  the,  70-A 

Magnetic  attraction,  57 

description  of  a,  compass,  64 
field,  43 
flux,  52 
lag,  54 


.NDEX  101 


M  ACNE  TIC— continued 

leakage,  55 
permeability,  49 
poles,  59 

power  of,  induction,  56 
saturation.  50 
traction,  58 

Magnetism,  history  oj,  41 
residual,  77 
theory  of,  40 

Magnetizing,  calculation  of,  coils,  67 

coil,  proper  way  to  insert  magnets,  66-A 
current,  65 
methods  of,  66 
wiring  of,  coils,  68 

Magneto,   cause  of  a,  sparking  at  the  safety  gap,  188 
cycle  of  electric  current,  12-A 
cycle  of  operation  in  a  high-tension,  18 
direction  of,  rotation  not  marked,  39- A 
effect  of,  lag  on  an  engine,  184 
electricity,  16 

flow  of  secondary  current.  28-C 
how  a,  is  timed,  37 
how  a,  is  timed  to  an  engine,  177 
how  to  find  the  direction  of  rotation  of  a,  39 
how  to  keep  a,  in  good  running  condition,  193 
how  to  oil  a,  194 
induction  of,   12-B 
pole  pieces  of  a,  60 
principle  of,  ignition,  20 
principle  of  operation  of  a.  17 
principle  of  operation  of  a  low-tension.  22 
principle  parts  of  a  high-tension,   15 
relation  of,  speed  to  distributor,   186 
relation  of,  speed  to  engine  speed,  185 
relation   of,    speed   to   engine   speed    on    a   9 

cylinder  rotary  engine,  198 
theory  of  a.  11 

the  term  high-tension,  defined,  14 
timing  range  on  a,  driven  at  ^  engine  speed, 

180 

timing  range  on  a,  driven  at  engine  speed,  181 
timing  range  on  a,  driven  at  I1/?  engine  speed. 

182 

what  is  a.  12 
what  is  a  fixed  spark,  28 
what  is  a  high-tension,  13 
what  is  a  low-tension,  21 


1.02 


MAGNETO  —  con  tin  ued 

what  is  a  polar  inductor,  24 
what  is  a  sleeve  inductor.  26 
what  is  a  starting.  28-R 
what  is  a  two  spark.  25 
what  is  a  unidirectional,  28-  A 
what  is  an  inductor  type  of,  23 

Magnetos,  what  are  synchronized,  27 
Micro-farad,  92 

Mixture,  indications  of.  a  lean,   173 
indications  of  a  rich.   172 

Molecules,  and  atoms,   10 
Ohm's  law  and  its  application.  142 
Oscillograph  diagrams,  83 
Platinum;  151 

Pole,  negative,  137 
positive,  136 

Potential,  difference  in,  97-A 

Resistance,  140 

action  of  ballast,  ,161 
unit   of  electrical,   141 

Rheostat,  143 

Safety  gap,  cause  of  a  magneto  sparking  at  the,  188 
what  is  a,  189 

Spark  advance  to  piston  travel,  relation  of,  183 
what  is  a,  95 
what  is  necessary  to  produce  a.  96 

Spark  plug,  cable,  how  to  locate  a  leaky,  107 
cables,  effect  of  misplacing,  190 
construction  of  a,  98 
electrodes,  setting  of,  101  I 
gaps  are  set  close,  why,  102 
gaps  set  too  close,  effect  of,  103 
gaps  set  too  wide,  effect  of,  104 
usual  causes  of  failure  of  a,  105 
what  is  a,  97 


INDEX  103 


Specific  gravity,  what  is,  119 

Storage  battery,  adding  water  to  a,   114 

buckling  of  the  plates  in  a,  122 

construction   of  a,  110 

difference  between  a  lead  type  and  an 

Edison,  116 

effect  of  charging  a,  112 
effect  of  discharging  a.  Ill 
electro-motive  force  of  a,  115 
electro-motive  force  of  an  Edison,  117 
how  the  capacity  of  a,  is  rated,  113 
how  to  test  the  density  of  the  electro- 
lyte in  a,  118 

how  to  find  the  polarity  of  a,  123 
leads  of  a,  120 
principle  of  a,  109 
proper  method  of   connecting  a,   to   a 

charging  circuit,  125 
sulphating  of  the  plates  in  a,  121 
what  is  a,  108 

Switch,  149 

cause  of  failure   in   a,  150 
ignition.  149-A 

Test  line,  description  of  a,  152 

Test  set,  description  of  a  buzzer,  153 

Timer  parts,  arrangements  of,  158 

Timing  lever,   manipulation.    178 

range  on  a  magneto.  180.  181.  182 

Winding,  ampere  turn  as  applied  to  a.  70 

difference  between  a  timer  coil  and  high-ten- 
sion, of  a  magneto,  164 
induced  voltage  of  secondary,  19 
ratio  of  primary  to  secondary,  79 
size  of  wire  on  primary,  80 
size  of  wire  on  secondary,  81 
variation  of  lag  in  a,  74 


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An 

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Primary  Coil 
A 


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